Evolution of the Chicken | Wisconsin Public Television

Evolution of the Chicken

Evolution of the Chicken

Record date: Feb 28, 2018

Mark Berres, Assistant Professor in the Department of Animal Sciences at UW-Madison, discusses junglefowl, four species of birds, which are possible ancestors of the modern chicken. Berres traces the domestication and cultural influences of the bird.

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Episode Transcript

- Welcome everyone to

Wednesday Nite at the Lab.

I'm Tom Zinnen, I work here

at the UW-Madison

Biotechnology Center.

I also work for UW-Extension

Cooperative Extension

and on behalf of those folks,

and our other cool organizers,

Wisconsin Public Television,

Wisconsin Public Radio,

the Wisconsin

Alumni Association,

and the UW-Madison

Science Alliance,

thanks again for coming to

Wednesday Nite at the Lab.

We do this every Wednesday

night, 50 times a year.

And tonight is the

start of our 13th year

so pretty happy about that.

Tonight, it's my pleasure to

introduce to you Mark Berres.

He works here at the

Biotechnology Center.

He's gonna be talking about

the evolution of the chicken.

He was born in

Centralia, Illinois,

which is in the central

part of Illinois.

[laughter]

But somewhere in his family,

somebody was smart enough

that by the time he

was in high school,

they moved up to

Eau Claire, Wisconsin,

which is where he graduated

from Regis High School,

and then he went over to the

dark side of the St. Croix

to go to the University of

Minnesota at St. Paul to get

an undergraduate degree in

genetics and cellular biology.

Then he saw the light and

came back to UW-Madison

to get his PhD in

zoology, a department

which no longer exists, he just

told me. Is that correct?

- It's now the department

of integrated biology.

- Well, that's even better.

Okay, he's been on

this campus since 1995.

You remember that.

And he's been with the

biotechnology center since 2016.

This is something we've all

been looking forward to.

This is Mark's second

Wednesday Nite at the Lab.

Please join me in

welcoming Mark Berres

back to

Wednesday Nite at the Lab.

[applause]

- [Mark] Thanks for

stopping by tonight.

As Tom indicated, we're

going to talk about the

evolution of chickens.

This is really at least

a similar foggy, in terms

of our understanding

of the origins

of these wonderful birds.

We're gonna discuss it

at some detail tonight.

It's a story that really spans

more than 300 million years.

And we're gonna cover

it from the basic kind

of origins of birds

themselves, then we'll jump

into a discussion of

chickens as a very

small group of birds.

There's really only four

species collectively termed

jungle fowl, that

are extant species.

I want to talk a little bit

about how they're integrated

into an understanding of

how our own human culture

has originated,

and in particular,

dispersed across the globe.

In fact, the evolution of

chickens, is extraordinarily

important for monitoring

human dispersal.

So a lot of anthropologists

make use of domestic animals,

not just the chicken, but the chicken is one of the more

interesting examples

of how humans

actually bring their

domesticated animals

with them when they

disperse to new areas.

And lastly, I want to

kind of talk about some

of the unknown trajectories,

in terms of evolution,

that the chicken may

actually be taking.

It's a very big challenge,

and we still don't know,

precisely, the complete story of

the evolution of the chicken.

It's unlikely that we ever will.

Unfortunately, it's

difficult to predict

where it's going as well,

and I'd like to give you

some perspective

on that as well.

So let's start about the

first aspect of birds,

for birds' sake.

The evolutionary origins

of birds, actually remain,

to this day, very obscure

and controversial.

And part of the complexity

arises from the fact

that we need to account for

not only birds themselves,

but also features

that they possess,

features such as feathers,

the ability to fly,

and even physiology

and behavior.

So most of us are probably

familiar with archaeopteryx

one of the oldest known birds.

It's about 145 to 150

million years ago.

It actually has features

so similar to modern birds

that they're actually

nearly indistinguishable.

Both Charles Darwin on the

left and his ardent supporter,

Thomas Huxley on the right

argued that archaeopteryx

was a sideline of

the avian evolution

and really not a

direct lineage leading

to any modern-day birds.

And indeed, the consensus

is, that's probably true.

Archaeopteryx is already a

bird in the modern sense,

at least 145 million

years ago, equipped

with flight adaptations,

including his wonderful

coat of feathers.

Unfortunately as such, it

can tell us very little

about the ancestry of

birds overall, particularly

for the early stages in

the evolution of feathers,

birds, and flight.

Since the discovery in geologic

dating of Archaeopteryx,

many other avian lineages,

as you can see here,

in fact, have been

discovered but all but one

are in fact extinct.

Nevertheless, archaeopteryx

is very important

for exploring the relationships

between modern birds

and reptiles, especially

with respect to skeletal

structures and most importantly,

the flight adaptations

that accrued over the

evolution of the bird

and also the timing of events

in the geological record.

And so the fossil record is

a great piece of evidence

that allows us to place

organisms and their lineages

on a geological time

scale and in fact,

it permits us to see

changes in diversity

in morphological

change over time.

The importance of the

availability that fossil

evidence simply cannot

be overly stressed.

It provides a morphological,

feature-based timeline

of evolutionary change.

But there's an insidious

problem with the fossil record.

Any sequence of events derived

from that fossil record,

is merely one hypothesis.

And the reason for that

is that the fossil record

is incomplete and

moreover, it's imperfect,

but nevertheless,

it's all that we have

and as scientists we

must use that in order

to answer evolutionary

questions.

Most of the major groups

of Mesozoic reptiles,

things like lizards,

pterosaurs, crocodiles,

and dinosaurs themselves,

have at one time or another

been considered the

ancestors of birds.

And after more than a

century, still to this date,

the ancestry of birds still

remains highly controversial.

Recent evidence which I

am going to present today,

actually seems to favor

a synthesis, actually

previously disparate

hypotheses rather than

any one single hypothesis.

So recall that the

amniotes are a group

of tetrapod vertebrates with

terrestrial adapted eggs.

Anatomically, amniotes

are characterized

by features called fenestra

which essentially are

holes in the skeletal

structure of any bone.

The diapsid reptiles have

in each side of their skull

two temporal fenestra behind

their eye orbits, right here.

And so except for

turtles and tortoises,

living diapsids are in fact,

extraordinarily diverse

and include all extant

crocodiles, lizards and snakes.

And there's one more

major lineage that we're

gonna get to in a few minutes.

While temporal fenestration

has long been used

to classify all of these

amniotes using the fossil

record, the function of

these fenestra have long

been debated and no

consensus has been reached.

Many believe that they

actually allowed muscles

to expand and lengthen

resulting in a jaw musculature

to enable better predation.

Others believe that they

actually house the pneumatic

sinus, which is in

fact, very important

in the evolution of

warm-blooded animals

because it's connected

to water vapor retention.

Despite those questions,

two lineages of diapsid

reptiles actually remain.

One group is the

Lepidosauromorpha which include

modern snakes and lizards.

The other group is

the Archosauromorpha

which actually gave rise

to a group of reptiles

called the basal archosaurs

or just more commonly,

the thecodonts, and

thecodont is the term

that I'll use for the remainder

of our discussion today.

The name, thecondont, itself

refers to the presence

of teeth that are set

in well-defined sockets.

Moreover, thecodonts are

specifically identified

by a fenestra in front

of their eye socket

called antorbital fenestra.

So geologically using

the fossil record,

we can clearly

identify, in most cases,

these types and

characteristics which enable

us to group these animals

in specific classifications.

The descendants of these

so-called basal archosaurs,

or thecodonts, include

crocodiles, pterosaurs,

and dinosaurs and certainly

our mystery group,

as we'll discuss,

birds themselves.

Now on the geologic time

scale, this area right here,

corresponds to about

300 million years ago,

towards the later portion

of the Carboniferous Period.

That's when all the tree ferns

and all the explosions of

the ferns had occurred.

The diagram shown here,

kinda shows the general

descent of the

thecodonts and in fact,

most scientists accept

the relationships

that are depicted

here regardless of

their specific views

on the origin of birds.

But two facets of this

figure actually create

substantial confusion that

I think it would be helpful

to our discussion.

Firstly, while pterosaurs

were indeed flying reptiles,

they are not at all

related to birds, in fact,

the wing structure

is a great example

that you'll find in every

basic biological textbook

of convergence.

Second are the terms

that are used to group

the two major

lineages of dinosaurs.

The term bird-hipped

or ornithischian refers

to the backward-facing pubis

or opisthopubic formation.

It's a characteristic of

many herbivorous dinosaurs

such as stegosaurus.

This term was used in

the older literature

because modern birds also

have a backward-facing pubis.

In this case, the confusion

arises as a terminological

rather than a

taxonomical relationship.

In contrast, the

reptile-hipped or saurischian

dinosaurs have a

forward-facing pubis.

These include the

herbivorous sauropods

and carnivorous

bipedal theropods

all of which are

classified as dinosaurs.

In general two theories of

the avian evolution exist.

First there's a

pseudosuchian thecondont,

or just plainly

thecodont theory.

This was postulated by

Robert Broom in 1913

and later championed by Gerhard

Heilmann, very smart guy.

Secondly there is just a

theropod, or a dinosaur

origin of birds.

This was actually

postulated by Thomas Huxley,

the contemporary of

Darwin back in 1868.

We'll talk a little

bit more about that.

But really, the

primary proponent,

after the acceptance of

the thecondont theory

was John Ostrom.

Unfortunately a full

discussion's gonna

take so much time,

so that we're gonna only

focus on Heilmann and Ostrum

because they're key players,

they weren't the originator

of the ultimate hypothesis,

Broom and Huxley were

and potentially others,

that's debatable, before them.

But throughout our

discussion, remember

that we actually need to

consider simultaneously,

not only the origin of birds,

but feathers and flight too.

Normally in a course

I used to teach,

it took about four

weeks to do that,

so we're gonna

burn through this,

but I think you're gonna be able to accept what we have to say.

The primary difference

between the two theories,

really are the specific

line of decent,

in other words, who

begat who, and the actual

timing of divergence.

Heilmann down here

believed that birds evolved

directly from a thecodont

or archosaurian ancestor

early in the Triassic Period.

Quite a different

theory was postulated

and championed by Ostrum,

he believed that birds

evolved from theropod dinosaurs,

which actually didn't

appear in the fossil record

until late in the Triassic.

Among Heilmann's

many accomplishments,

he also advanced an arboreal

model of feather evolution.

Feathers were adaptations

to improve aerial gliding

capability, ultimately

leading to flapping flight.

And so for this theory

actually to work,

an avian ancestor must have

been able to climb trees,

such as depicted in

this cartoon here,

and we'll come back to

this, so that it could

actually use gravity

to accomplish flight.

On this basis alone, Heilmann

considered a dinosaur,

a thecodont, I'm sorry, wait,

that was a big faux pas,

that is a thecodont,

not a theropod, a

key to bird ancestry.

The quadrupedal motion

used by euparkeria

enabled it to climb

trees where he believed

that flight could have evolved

under this so-called

arboreal model.

It had other anatomical

features consistent,

skeletal features, that are

found in modern birds as well.

And so, when he first

postulated this synthesis,

this idea of an

arboreal avian ancestor

sat really well with

most researchers.

After all, so the argument went,

it makes aerodynamic sense

for key flight adaptations

to evolve arboreal, where

gravity is your friend.

So then Heilmann really

argued that birds

evolve directly from an

ancestor of those thecodonts

early in the

Triassic euparkeria,

not that birds descended

from dinosaurs or theropods,

which occurred at time

much later in the Triassic.

Well from the time that

he postulated that,

his theory actually

remained strong and

relatively unchallenged

until 1973 when John Ostrum,

based on newly-acquired

fossil evidence, revived

Thomas Huxley's original

theropod, or dinosaur

origin of birds.

Ostrum refined Huxley's

theory and suggested

that a specific

subset of theropods,

these so-called Dromaeosaurs,

like deinonychus

and velociraptors, were

the ancestors of birds.

Now I have to

digress for a moment.

You're all familiar,

likely, with the movie,

Jurassic World, Jurassic

Park, et cetera, et cetera.

You all remember

the velociraptors.

Does that look like

the velociraptor

that you actually

saw in the movie?

No, in fact, they call

that velociraptor.

In fact velociraptors were

probably about the size

of a small turkey or

so and deinonychus,

kind of the

quintessential dromaeosaur

that Ostrum used to

forward his theories,

was in fact, what's

represented in that movie,

although I think deinonychus

is not as cool sounding

as velociraptor.

Nevertheless, it

really broke my heart

when I saw that because

now I can't believe

everything that I see on

television and in movies.

[audience laughs]

In any case, in contrast

to Heilmann, feathers were

essentially co-opted for

flight, having in Ostrum's mind

originally serving an

insulative mechanism.

And so Heilmann believed

that feathers actually

evolved in terms of the

acquisition of flight,

through his arboreal model.

In contrast, Ostrum

believed that feathers

had nothing to do

with flight at all

and only later in the evolution

of feathers themselves,

were they co-opted to actually

serve a flight function.

So you should be

able to see now,

you gotta worry about not

only birds themselves,

but how feathers

came onto the scene,

how flight evolved, et cetera.

But one major objection

to Ostrum's theory

was the obligate bipedal

nature of theropods.

Essentially, people

asked how do you get

a bipedal theropod up a tree?

It's not easy.

[audience chuckles]

A key piece of evidence

supporting this objection

was the fact that

theropods actually have

a forward-facing pubis

which would definitely

interfere in their

ability to climb trees.

That is in addition to

actually trying to just use

two feet or maybe using your

forelimbs as well to do it.

Perhaps most damningly,

the acquisition of flight

from ballistic jumping,

or so-called ground up,

or cursorial mode of

evolution in the acquisition

of flight, that

was just equivalent

to aerodynamic

heresy at the time.

That's a big story, it is

still continuing to this day.

But most importantly,

there was always a big

problem at the time Ostrum

was promoting his hypothesis.

The oldest bird, archaeopteryx,

was older than any

of the feathered

theropod dinosaurs

that were previously found

typically in the range

of around 25 to 30

million years, therefore,

the critics of Ostrum claimed

that feathered dinosaurs

could not have been

ancestral to birds

because all feathered

dinosaurs thus far discovered

were younger than archaeopteryx.

Well, really Ostrum's

theropod dinosaur theory

has always been

troubled by the absence

of those feathers on dinosaurs

older than archaeopteryx,

but what did I say earlier

about the fossil record?

It's imperfect and incomplete.

All you have to do, pun

intended, is wait a little while

and you're gonna

have a discovery.

And in fact, in 2009 an

incredible find in China

provided the critical

last bit of evidence

that really tended to suggest

that Ostrum was,

in fact, correct.

Anchiornis huxleyi, a

completely feathered theropod

was found and dated to

about a geological time

of 164 million years,

which is much older

than archaeopteryx itself.

Archionics, I'm sorry,

anchiornis is a troodontid.

You can see it's just a tiny,

little ankle-biter here.

It's a small, very

small sized theropod.

It had unusually long legs

compared to other theropods,

consider birds of modern day

and with a large curved claw

on retractable second

toe, right here.

This is very similar

to the sickle claw

of the dramaeosaurs, like

deinonychus that we saw earlier.

Troodontids also have

some other features

that correlate with

modern day birds.

They had unusually large

brains among the dinosaurs.

Their eyes were

also unusually large

and pointed forward,

indicating that they probably

had some good binocular vision,

just like birds today.

The ears of troodontids

were also different

from other theropods

having extremely enlarged

middle ear cavities,

indicating possibly

a very acute hearing ability.

Now, in the past 20 years,

hardly a week goes by

without reports of newly

discovered fossil birds

adorned with all

types of feathers

and they are, in general,

many of them are in fact,

much older than

archaeopteryx and all of them

are classified as theropods.

This one was just recently

published earlier this year,

last month, in February.

This is a fossil image of

a bird called caihong juji,

which I believe

means rainbow crest.

It actually was demonstrated

to have iridescent

plumage, in other words,

highly organized substructures

of melanochromes which

give, hummingbirds is gonna

be the best example

here in Wisconsin,

that beautiful iridescence

on their gorget.

This continues to happen,

primarily out of Mongolia

and that is the happening

place for this type of work.

But Ostrum still faced

the problem of how to get

an obligately bipedal

theropod up a tree.

And so if he could only

assert that a small size

bipedal theropod

could actually somehow

gain access to the trees,

the arboreal model,

that at the time

everybody preferred,

that model ensues automatically.

And evidence suggests

that these theropods

were probably coelurosaurs

which included the dromaeosaurs.

Compsognathus was a

coelurosaur and was probably

at least facultatively arboreal.

Now I know if you saw

Jurassic Park 2, you all saw

what a little

compsognathus looked like

that was on the beach that

attacked that little girl

on that island and

essentially compsognathus

was actually the

dinosaur, the coelurosaur

that Thomas Huxley used

and actually compared it

to the modern-day

chicken that allowed him

to formulate his theories,

to actually consider

that in fact, there was a

dinosaur origin to birds.

So by allowing that

bipedal theropod

to climb a tree, we

can actually eliminate

a very complicated

cursorial or ground up model

for the evolution of flight ensuing an arboreal model.

Well a new, relatively new, about 20 years ago or so,

theory to explain how a

bird's flight apparatus

first evolved is that it's

forelimbs may have added

traction to run up

inclined slopes like trees.

And so no one is

actually postulating

that a bipedal organism

just uses its feet

to run up the tree, forelimbs

were actually involved.

And in fact, the forelimb,

the apparatus in birds,

has been extensively remodeled

in order to accommodate flight.

A researcher named Ken

Dial in Montana observed

the behavior of chukar

partridges, chicks essentially,

as they ran, and adults

too, and worked out

why they actually flap their

wings during climbing events.

He found that birds

employed something called

wing-assisted incline running.

Here the flapping motion

of the bird's forelimbs

did not lift the birds

as if it were to fly,

but rather quite the opposite.

The flapping action actually

resulted in the physical

force that pressed them

downward for better traction,

much like spoilers work on

high-performance race cars.

He found that even day-old

hatchlings can easily

traverse inclines of up to

45 degrees without flapping.

They just kind of move

their unfeathered,

well at least

downy-feathered forelimbs,

but if they flapped they

could actually scale

greater slopes so

hatchlings could

climb a 50 degree incline.

Four-day old chicks could

climb a 60-degree slope.

Twenty-day old chicks

could actually climb

a 95-degree slope, an

almost vertical surface.

Adults can get up to

105-degree overhang

and it's just by flapping

and they're not using

their wings to

actually gain flight.

This is to gain traction.

I gotta throw this in here

because this is so cool.

I just put it in just a few

minutes before I came in here.

In 1985 Walter Bock

elaborated upon a hypothesis

published originally

in 1880 that suggested

flying originated in

small arboreal quadrupeds

similar to euparkeria,

that may have jumped

tree-to-tree or tree-to-ground,

for any variety of

reasons, feeding,

predator avoidance,

mobility, et cetera.

This later became

the arboreal model

of flight evolution that was

championed by Gerhard Heilmann.

After all, there were all kinds

of non-flighted animals

that do just this.

You can actually go outside,

lemurs, flying squirrels,

even reptiles like

snakes, okay, contributed

to his understanding of a sequence of evolutionary

form change that would

enable possibly birds

to acquire flight.

Walter Bock elaborated

Marsh's theory,

which was originally, he

was the credited originally

to the arboreal flight

model back in 1880,

to depict an evolutionary

pathway following

a simple and direct route

without these so-called

hopeful monsters or those

organisms without elaborate

intermediate evolutionary steps.

These steps included

climbing the tree,

jumping off a limb,

parachuting, gliding,

eventually acquiring

powered flight.

He explained the adaptive

value of arboreal life

in this, it's really cool,

it's called the invasion

of trees model and it's really

regaining a lot of traction.

In 2003 the best evidence of

a tree climbing, feathered,

facultative biped,

bird-like theropod was

in fact, named microraptor gui.

Take particular note

of its shape.

Does this remind you of

Bock's gliding animal?

I mean look at this.

This was done in 1985 before

any such fossil evidence

of an animal similar or near

the anatomical structure

of microraptor had

ever been known.

I mean this is a

classic prediction

followed by observation.

This is what science

is supposed to be,

that's why I had to

throw that in there,

a plug for science.

Despite the way Heilmann

and Ostrum are used

in a mutually exclusive

manner, it now actually seems

that they were both

right and both wrong.

I wouldn't really

fault them too much

because they really had to

work with extraordinarily

complicated composite

hypotheses requiring them

to simultaneously account

for the origin of feathers,

birds themselves, and flight.

That's a lot to deal

with and at the time,

the information that we have

available was not available.

Nevertheless the

most recent evidence

that we've acquired just

in the past 30 years or so,

supports a more unified theory

and I've got that

depicted over here.

After more than a

century, recent evidence

supports a more unified

composite theory.

Birds, chickens as we'll

see in the next few slides,

are derived from theropods,

which themselves are

egg-laying reptiles that

originated around some

216 million years ago.

The first unequivocal

bird archaeopteryx,

which appeared on the scene

around 145, 150 million

years ago, yep,

bird, but in fact,

did not give rise to

modern birds per se.

And the modern birds

actually evolved

from a group of

carnivorous dinosaurs

called the dramaeosaurs

which were around

around 120 million years ago.

These are some examples

that we've discussed,

to include velociraptor,

deinonychus,

anchiornis, and the like.

So the diversification of

these proto-avian forms

actually occurred vary

rapidly until the onset

of the Cretaceous

extinctions here

at around 65 million years ago

when nearly all

dinosaurs went extinct.

So these are all kind of

the bird-like organisms

in this area here.

A small group of dinosaurs,

of theropod dinosaurs,

the so-called transitional

shore birds did survive

and then quickly diversified

into the 10,000 or so

modern bird species that

we actually see today.

And so indeed, now you know,

really, take my word for it.

Birds are truly the only

remaining lineage of dinosaurs

that in fact, survived

the Cretaceous experience.

The dinosaurs never went

extinct, they changed.

They evolved into

birds themselves.

But all of the incredible bird

diversity that we have today,

only four species, collectively

called jungle fowl,

are considered ancestors

of the modern chicken.

Jungle fowl belong to

the order galliformes,

which includes all of

the pheasants and quail.

It's a small, it's

not the biggest order,

around 214 species or so,

but the special feature

which distinguishes jungle

fowl from all other birds,

is the presence of both

the presence of a distinct,

enlarged cone and

accompanying waddles

and there are a tremendous

variety of these in existence.

The jungle fowl, as a whole,

are widely distributed

across Central and Southeast

Asia, but each species

tends to have a specific

habitat preference.

The red jungle fowl

has the largest range

of the forest species and

in contrast to the others,

red jungle fowl exhibit

marked geographic variation,

especially in male plumage.

Females do not exhibit

that much variation

in their plumage

characteristics.

All of these jungle

fowl are omnivorous

and they all exhibit

behaviors that are essentially

like those that we see

in modern domestic fowl.

One key difference, however

though, is their vocalizations,

particularly males

differ considerably.

Jungle fowl typically

breed once per year,

laying only clutches of

around four to eight eggs.

Curiously, red jungle

fowl also have white skin,

while most domestic

chickens have yellow skin,

including the gray jungle

fowl and that's going to be

really important in

just a few minutes.

So, unlike the

sequence of mammalian

domestications which

are fairly well known,

the origin of the

domestic chicken,

just like the origin

of birds themselves,

is very controversial and has been debated forever.

So not only has the site

and timing of the first

domestication event

remained contentious,

but because multiple

species of jungle fowl

exist in close proximity,

the possibility

that domesticated chickens

originated from multiple

wild ancestors also

remain unresolved.

And so there are

three major questions,

there's hundreds of

questions, but three major

questions that have perplexed

researchers and people are

actively investigating

this, are domestic chickens

derived exclusively

from one of these

extant breeds of chicken?

And we'll see that

most people believe

that red jungle fowl

was the ancestor.

Alternatively, did others,

did any of the other species,

any of the other three,

or were there any other

closely related species that

actually made a contribution?

And where did people first

domesticate chickens?

And when did this occur?

These questions and the

answers, more importantly,

to these questions

have much more meaning

than just evolutionary

importance.

They can provide insight

into our own history

and I'm gonna show you a

number of examples of that.

And each has implications

in both the use of chickens

as model for biomedical

research and also revealing

a genetic basis for rapid

evolutionary adaptations,

essentially the

foundations of our modern

animal and plant agriculture.

For example, nearly all

modern chicken production

depends on two breeds of

chicken, the white Cornish

and the single

comb white leghorn.

Incredibly only after about

sixty years of intensive

agricultural selection,

efforts have yielded

these powerhouse birds.

We'll talk more about that.

I want to talk a little

bit about the basis

of how Darwin believed that

through character differences

in the fossil record

and also cross-breeding

experiments, Darwin

concluded that the domestic

chickens were derived

solely from red jungle fowl.

And he did this in "The

Variations of Animals and Plants

"under Domestication," which

was published in 1868.

In that argument, he also

based some of his evidence

on translations of Chinese

documents published in 1609,

which indicated to

him that chickens

were first domesticated in

China at around 1400 years B.C.

These actually,

these beliefs again

were relatively unchallenged

when early in the 1940's,

they began to receive

some criticism by a

number of researchers

who believed that perhaps

two, three, or all four

of the varieties of different

jungle fowl may have

contributed to

chicken domestication.

Moreover, these same authors

that were challenging

Darwin, also believed that

chickens were first domesticated

much further to the west,

here in the Indus Valley,

in near modern-day Pakistan, around 2,000 B.C.

And this is a belief

that prevailed throughout

the latter half of

the 20th century

and still is fairly

commonly cited to this day.

The answer to the species

contribution question

may have actually been answered.

The majority of chickens

used for commercial egg

and meat production

have yellow skin.

The occurrence of the yellow

skin, and also in the legs,

is influenced by the

amount of carotenoids,

which is a type of a

xanthophyll, in the feet.

More carotenoids produce

more intense yellow color,

a condition that's

favored by many consumers.

And in fact, in the

modern chicken industry,

marigold petals continue to

be used in certain areas,

to control the

color of egg yolks

because people have a

preference for the intensity

of the yellow pigmentation,

which are carotenoids,

in egg yolks.

Nevertheless, researchers

evaluating the origin

of yellow skin in

modern day chickens,

they discovered that

in fact, is was caused

by a recessive regulatory

mutation in the gene

called BCDO2,

which is beta-carotene

dioxygenase 2, in skin.

Essentially, that gene

cleaves yellow carotenoid

pigments into colorless

byproducts, thus a reduction

in the expression of that

particular gene, BCDO2,

produces yellow skin

because there's nothing

to cleave the carotenoid and

result in that yellow color.

Essentially this is a recessive

loss of function and mutation.

Now researchers concluded

that yellow skin

must be a hybrid trait

resulting from a cross

between gray jungle fowl

and red jungle fowl.

There remain some

questions to this research

including the extant

crosses of red jungle fowl

to gray jungle fowl tend not

to produce fertile hybrids.

There's a lot of contention

and there are some issues

regarding the source

of the red jungle fowl

and the gray jungle fowl

actually having been

contaminated by the introgression of modern day

genetic elements

into their genome.

There's also an

issue where hybrids

in which the BCDO2

allele exists,

we don't know whether

the yellow skin

or the white skin allele

of that particular enzyme

is ancestral or derived.

So their evidence is

pretty good to suggest

that there's a hybrid origin

of our modern chickens,

but it's by no

means a closed case.

Up until 1988, most

people believed

that the domestication

site, as I said, occurred

in Central Asia in

the Indus Valley,

but new archeologically-driven

evidence provides

a new interpretation

of both when and where

chickens were

first domesticated.

The anthropologists

actually use carbon-14 data

from bones found

essentially in trash piles,

again because of the

unique internal structure

of avian bones, they

can discriminate bones

that were derived from birds

and presumably chickens,

from mammalian bones.

And what these researchers

found was that over 16

archeological sites in

China, here, actually

predate the Indus Valley

carbon-14 date of birds

by about 4,000 years.

Moreover, at least 13

sites have been identified

much further to the west

in Europe and Western Asia,

all of which also are

older than those bones

that were in fact, found

in the Indus Valley.

And so the reason for

that are two trade routes,

a northern route and

a Mediterranean route,

are thought to have supplied

the western cultures

with domesticated chickens.

And by 100 B.C. essentially

chickens were everywhere

across western

Europe, but strangely,

despite the two trade routes,

maybe you can see,

India actually was

bypassed completely

and did not acquire any

domesticated chickens

until much later

in human evolution.

One curious aspect is

that the site of Chinese

domestication did not

overlap the extant range

of red jungle fowl and this

has important implications.

It means that either

the present range

of red jungle fowl has

contracted somewhat,

alternatively, red jungle

fowl were obtained elsewhere,

so perhaps more southerly

area and moved northward

into China and which

has a corollary

in that red jungle fowl actually

domesticated by cultures

elsewhere and then subsequently

transported to the Chinese.

Let's move to our

side of the world.

Analysis of the

cultural diffusion

of domestic chickens

has intriguing relevance

to our side of the globe too.

The presence of chickens

in the American continents,

both North and South

America, traditionally has

been attributed to

Spanish introductions

of European chickens

after their arrival

in the mid-portion

of the 15th century.

However, there is

very heated debate

about whether Amerindians

in South America

possessed chickens before

the arrival of the Spanish,

particularly in relation

to several unusual Chilean

breeds that lay blue-shelled

eggs and possess

distinctive plumage

patterns, namely ear tufts

and the lack of a rump.

The possibility of

chickens being present

in the Americas,

pre-Columbian, continues

to gain traction

having been popularized

by a number of books

by Gavin Menzies.

He actually believes

that pre-Columbian

contact with the Chinese

in the early 15th century

provided chickens to the region.

Other researchers

actually link linguistics,

cultural artifacts, cultural

use, primarily religious

ceremonial use, and

names for chickens.

They actually suggest

contact with Asia

much, much earlier than even

Gavin believes had occurred.

Based on mitochondrial

DNA sequences,

and again carbon-14

dating of chicken bones

that were discovered in middens,

a New Zealand group

claimed firm evidence

for a pre-Columbian introduction

of chickens to the Americas.

In one particular bone

obtained in Chili, here

a mutation was discovered

that also occurred

much further west in the

Pacific along and among

the islands of Tonga,

American Samoa,

which are actually dated

to times much earlier.

And so the idea was

that the well known

seafaring activities of the

Polynesians kinda fit well

with this genetic

mitochondrial DNA evidence.

Anthropologically, this

evidence was really intriguing

because of speculation of

ancient Polynesian contact,

which itself was popularized

by the voyage of Kon-tiki.

Some of you probably

remember that.

I think it was a Norwegian guy.

He was going in the opposite

direction, I believe.

He was going from South

America to Polynesia,

but nevertheless, it's

a sensible connection.

In particular, Easter

Island, Rapa Nui,

is very important because

it may have facilitated

the contact, essentially,

kind of the trans-shipping

point of people

between Polynesian

and South American cultures.

As such, the New Zealand

researchers went on

to conclude that the

South American chicken

had been introduced

by Polynesian voyagers

way before our first

European contact,

probably around in 1300's or so.

Well, later that year,

a challenge was posited

by a completely different

group, an Australian group.

Those guys conducted a

much more elaborate study

and concluded very

vociferously that there was

absolutely no support for

Polynesian-South American

contact as indirectly

derived from analysis

of DNA sequences

and carbon-14 data.

Their primary evidence

was that a Pacific

and Chilean pre-Columbian

chicken sequences

fall into a

particular haplogroup,

which just means a

variant or an allele

of the mitochondrial

DNA sequence,

which actually consists

primarily of widespread

Indian, European,

and sub-continental

Chinese haplogroups.

And so importantly,

haplotype E would have been

introduced by the Spanish

in the 15th century

as well as with many

European breeds being

transported subsequently

to the Americas

through the colonial era trade.

But in agreement with

the New Zealand group,

the Easter Island

specimens were classified

as pre-European,

but none of those

Easter Island haplotypes

have been detected

in either ancient or modern

South American chicken breeds.

And even if they did,

their study concluded

that there is no evidence

at least supporting

that they persisted, so

they may have made it there,

but we don't know

because none exist today.

There was also the

matter of the, an issue

with the carbon-14

data being affected

by seawater isotopes.

This group claimed in

fact, that their carbon-14

dating information was

biased to be much older

than it actually was.

We don't have time

to talk about that.

It's reasonable, but it's

still acrimonious at best.

We're finding further

ancient DNA techniques.

The Australian group

further expanded the study

and showed that the

individual bone used

previously by the

New Zealand group,

to link Easter Island

and South America was

in fact, contaminated

by exogenous DNA.

Unfortunately this

is monumental problem

with ancient DNA

studies, but fortunately

standardized protocols

have since been developed

which minimize, but they

do not eliminate these

types of problems.

So, in fact, we do

this type of work here

in the Bio-Tech Center.

We need suits and everything.

It's quite an

involved procedure.

Additional analyses performed

by the Australian group

reaffirmed connections

between chickens

off of the mainland and

throughout Micronesia,

but in fact, no evidence

of any chicken haplotypes

ever went further east.

For now, they stopped

at Easter Island.

Let's switch gears a

little bit and talk more

about kind of more of a

modern age of chickens.

And so when most

domesticated animal species

were used from the

beginning as a food source,

some, like dogs,

cattle, and horses,

primarily served

as work animals,

but the situation with

chickens is actually

considerably different.

Archeological and

historical records indicate

that the first use of

domesticated chickens

was actually cultural,

particularly in religious

and superstition

ceremonies, decorative arts,

and in fact, at

least what they call,

entertainment,

namely cock fighting.

Only much later were

chickens utilized

as source of human food.

The oldest form of

entertainment was undoubtedly

cock fighting.

Male jungle fowl

naturally fight and it was

this innate tendency

that actually, probably,

somewhat possibly, who knows,

contributed to the first

domestication efforts.

Breeds like the Assil

here and the Shamo

are testaments to the

efficacy of selection

efforts put forth by

their human breeders.

Some of you, any

presidential historians here?

You probably all heard the story

about Honest Abe Lincoln,

that one in fact,

there is some evidence

to suggest that

that's a sanitized

interpretation

because he had

returned some money

from an individual who

had overpaid at a shop,

in fact, I'm trying to confirm

this, I don't know if it's true.

I'd love to get an

email or a phone call

from someone who is an

expert in this area.

But in fact, the

moniker of Honest Abe

actually came from

Abraham Lincoln's ability

to fairly judge cock fights

in early American history.

Not sure, I'd love

to find out for sure.

Manipulated for

thousands of years,

there are now hundreds,

if not thousands,

of chicken breeds in existence

throughout the world.

They're roughly

divided by primary use,

whether for eggs or meat

or ornamental purposes

and with some of the being

considered dual purpose breeds,

like for both

eggs and meat.

Commercial chicken breeders

have an impressive record

at improving the

efficiency of egg and meat

in poultry production,

which has actually

helped to make poultry

products affordable

and available for, excuse me, consumers worldwide.

Incredibly concerted

efforts to improve

significantly the chicken

for use in US agriculture

only had taken

place very recently,

starting after just World War I,

but primarily in the years

following World War II.

Along with their

important use for food,

chickens also play

a critical role

in improving human health.

Right here on campus,

they're are many researchers

advancing our understanding

of biochemical

and disease processes

using chickens

as biomedical models.

Moreover, just in time

for the later portion

of the influenza season, thank

a chicken for the vaccine.

Even though it may not have

been perfectly effective,

it was still made from

hen's eggs in its entirety.

Over the last 50 years,

since World War II or so,

genetic selection

in poultry has been

proven to be

extraordinarily successful

resulting in specialized

egg laying breeds

and fast-growing meat

breeds that far exceed

the production of

their wild ancestors.

Approximately 60

breeds or so of chicken

that have been raised

in the United States

post-World War II,

actually were abandoned

by commercial

enterprise in favor

of just a handful of

very high performers.

Today five industrial

breeds of chicken supply

almost all of the chicken

meat and brown eggs

and white eggs sold as

food across the world.

Layer strains are obviously--

are mainly selected

for high egg output and

efficient feed conversion.

White eggs, now, come

almost exclusively

from a single breed

of white leghorn

and brown leghorns are

derived from breeds

related to Rhode Island reds.

Today hens from modern

layers can produce

on the average of

nearly 300 eggs per year

which is a far cry

from a single clutch

of four to eight of the

wild red jungle fowl.

Under a commercial perspective, the general breeding goal

for chickens or any farm

species for that matter,

is balanced performance

profile suitable

for efficient production

of meat or eggs

under the prevailing or

expected future conditions.

Poultry breeding

is no different.

It's part of the food chain

and goals have to be defined

according to the expected

demands of consumers

and those who produce and

market the animal products.

Increasing the tension to

agricultural sustainability

in farm animal breeding

includes the objective

to produce animals

under conditions

which meet ethical

standards of society.

And one key aspect of this in

fact, is disease management.

In an era with increasing

environmental change,

particularly the emergence

of exotic infectious agents,

we should really be on

high alert about the

immunocompetence of our

agricultural animals.

Intensive selection has

reduced genetic variability,

the raw material for

evolutionary adaptation

which has profound

impacts, not only for the

well-being of our ag animals, but also for our human society.

One example that if

you were here in 2015

in the Midwest, was the

widespread occurrence

of a high path H5N2

avian influenza epidemic.

At least 60 million birds, chickens, and turkeys,

and probably much

more than that,

were actually destroyed

and in doing so,

incurred more than a $3

billion economic loss,

just within this country.

But with regard to

immunocompetence,

genes, for example,

in the major

histocompatibility locus

play an important role in

not only immune responses

of animals but us as well.

It is responsible for the

resistance of many sources

of disease including

viruses, bacteria,

and even internal and

external parasites.

To answer the question

if selective breeding has

reduced the level

of MHC variation,

which in and of itself

is a good thing,

we assayed more than 1,300 commercial broilers and layers

that were derived from

multiple commercial

and research lines

and we found actually

78 unique haplotypes, or

different forms of the MHC

locus that were actually assigned to 22 families.

Analysis of that data

showed that our approach

was sufficient to

identify all previously

identified haplotypes,

which was done serologically

by a scientist named

Briles down at UI-UC.

But we were also

able to differentiate

many new haplotypes.

At this time the

work was completed,

we actually concluded

that lots of MHC diversity

exists in domestic chicken lines

and the connection

to the health and MHC

of an organism is

really in terms

of disease resistance.

A lot of variation

in the MHC loci

are gonna provide more

opportunities to combat

diseases whether

they're bacterial,

parasitic, or viral in origin.

Together with a former

student of mine, Hoa Nguyen,

we actually designed a

project to assess MHC

variability in the ancestors

of the domestic chicken.

The reason that we did that

is because the evaluation

of the MHC haplotype

variation in commercial,

highly-derived lines was

essentially an N of 1,

we just saw what was in fact,

in these commercial lines.

We had no idea

what was available

in terms of allelic

variation in other chickens.

We actually focused our

efforts in the Annamite Range.

This is a plateau in

south central Vietnam.

It's extraordinarily

topographically diverse

and it supports an

amazing diversity of life

and particularly

phasianinates, or chickens

and pheasants and

quails, extraordinarily

diverse here and very abundant.

I suspect that this

is probably a species

diversification

center where in fact,

the chicken may have indeed

been first domesticated.

Nevertheless, within

the Annamite Range

and surrounding areas,

we captured hundreds

of red jungle fowl from

four different ecotypes.

There's Hon Ba here which is kind of a deciduous forest

in the foothills of

the Annamite Range,

similar to types of

forests that we have here,

but much more diverse

floristically.

Yok Don is further inland

adjacent to the Cambodia,

it's very dry, seasonally

dry, deciduous forest,

seasonal fires, red

jungle fowl are everywhere

in that particular area.

This is almost totally devoid

of human habitation as well.

Lowland areas in

Cat Tien, this area

produces the best

protected habitats

of typical lowland rainforests

in the Southeast areas,

bamboo forests predominate,

again, abundant

with red jungle fowl,

they love bamboo.

And then Lo Go Sa Mat,

this is also an area

that borders Cambodia.

Now this one's

moderately disturbed

as human activity is

common in the area,

but nevertheless, there

seems to be relatively

undisturbed population

of red jungle fowl.

There's one, this

guy right here,

this is Cambodia here,

this is Vietnam here.

That guy would cross without any

impunity going back and forth.

He'd go over here for the day and then at night he'd come back

and nobody cared.

[audience laughs]

Anyway, importantly,

these areas were protected

and with the exception

of Lo Go Sa Mat,

they were very remote

as to avoid any genetic

introgression from

domestic stocks,

that plagues studies that

compare so-called jungle fowl.

Many of these species,

specifically the birds that

they use in these studies,

have been introgressed

with domestic species.

Great time, really hard

work, we received a lot

of assistance from

a lot of the locals

no matter where we went.

This is Mr. Ha, he

could draw blood

like nobody's business out of

a bird, never used a syringe.

He had the steadiest

hands I've ever seen.

Mr. Ton, again, he was the

one who kind of told us

that our trapping

techniques were moronic,

I think was the translation.

[All laugh]

And he was absolutely

correct because we thought,

oh, yeah, we're gonna

use what we use to like,

collect sage grouse or

greater prairie chickens,

these little cloverleaf traps.

They work really

well here in America.

You bring those over to

Vietnam, the chickens they

look at 'em, pfft, no.

They're way smarter

than any thing

that we have over here.

Mr. Ton really taught

us how to actually

capture these birds.

We even had a lot of the

forest service people

in some of these

areas help us out too.

These guys are practicing on

a domestic species of bird.

It was really a

great collaboration

between Hoa and myself.

Hoa is native

Vietnamese National

and it was the

funnest time, I think,

of my life in that area

doing that fieldwork.

In any case, interrogating

that MHC locus

in the same manner as before,

the results of the red

jungle fowl analysis

were really quite striking.

Without any doubt, even

though we did discover

some MHC variations

in domestic lines,

it was a far cry of

what we uncovered

in red jungle fowl

across those four areas.

This information really

prompted a reconsideration

of what MHC diversity

actually really means.

We expanded the study to

domestic heritage breeds.

So these heritage

breeds are those modern

domesticated chickens but

tend to be not selected

intensively like our

commercial breeds.

Heritage breeds are diminishing

but still are present

worldwide, they're everywhere.

In particular the

Finnish Landrace breed

that we investigated

actually traces its origins

almost a thousand years

ago with multiple lineages

maintain of small populations

in isolated villages

typically by very

wealthy people.

In Finland only the

wealthy could actually keep

chickens historically,

but certainly that

has all gone away.

The breed is

extraordinarily well-adapted

to cold, Finnish climates.

They're very broody hens and

very infrequent egg layers,

but they can forage like

nobody could ever believe.

Conservation efforts to

protect this endangered species

actually initiated by a

hobbyist breeder in the '60's.

A national conservation

program was established

near 2000, I think it was

1998 or something like that,

and now consists of at

least 12, there's many more

actually now, different

populations that are

currently maintained

by a network of amateur

hobbyist breeders.

In the 12 Finnish samples,

I'm sorry, in the 12 Finnish

Landrace populations we

sampled, we found 36 haplotypes.

16 were known previously

from the domestic

commercial and research lines.

There were none in common, in

fact, we have not found any

MHC haplotypes in common

with the red jungle fowl

that we kept from Vietnam.

The 16 that were actually

previously reported,

had been seen in New

Hampshire, Rhode Island,

reds and white leghorn breeds,

suggesting that there was

actually introgression

with the existing

domestic stocks

that were imported into

Finland post-World War II.

We moved over to Germany.

We sampled approximately

1,500 individuals

from German heritage breeds.

There we discovered 104

haplotypes and in this sample,

only 20 were known

previously, which leaves us

with an abundant 84

novel haplotypes.

We're currently

assessing haplotypes

from chickens in other

parts of the world,

namely, Africa, Asia,

and also the Caribbean.

So earlier I mentioned that

most of the MHC haplotypes,

even those that have

been known for decades,

were not associated

with any particular

disease resistance.

We know that MHC confers

resistance to diseases,

but we don't have a lot

of evidence of specific

haplotypes conferring

resistance.

There's one exception,

it's the B21 haplotype

which confers resistance

to Marek's disease,

a really nasty disease

that affects chickens.

Those of you that keep

chickens as backyard here,

when you order your

chicks, you always say,

do you want a Marek's

vaccination, check

"yes," definitely.

But clearly whatever immunity the Midwestern chickens

had during that H5N2

outbreak in 2015

was not sufficient

to protect them.

But we have seen

tremendous MHC diversity

exist not only in

the progenitors of

domestic chickens,

the red jungle fowl, but

also the heritage breeds

living throughout the

world and also living

in many different and

disparate environments.

And so combined with

genetic information,

I really believe that

kind of a phenotype,

genotype connection

will be more emergent

and accessible than ever before.

This is important because

the loss of genetic

diversity will not only

decrease the ability

of chickens, and

really all life,

to evolutionarily respond

to environmental change,

but will also likely

sacrifice useful

biological information, such

a stock genetic diversity

and a suite of

potentially important novel

and as of yet, untapped

genetic resources.

But we have to take

the appropriate steps

to protect these valuable

genetic resources.

We need to preserve and

study what we have remaining.

For example, who knows

what the MHC in that guy

looks like? [audience laughs]

This is a breed, it's

called the dong tao.

It's a heritage

breed in Vietnam.

These birds are typically

purchased around

holidays, namely Tets,

Christmas time here.

Birds like this guy,

this guy was selling

in Ho Chi Minh City,

Saigon, $3,000 US.

That's a cheap one.

[laughs]

Very expensive, so this is

a culturally driven breed.

You might think, oh

my god, that bird has

the worst mite infection

I've ever seen.

No, it's not, in fact,

those are not mites,

that emargination of

the scales is genetic

and so these are

not pretty chickens.

Beauty is in the

eye of the beholder.

Nevertheless, my point

here is to understand

that it is for you to

understand and appreciate

that while we have all

these great animal,

agricultural enterprises are

that we have to be cautious

about what we're doing to them.

Until 2015, the prevailing

attitude about high path

avian influenza

affecting the chicken

and the turkey products

on the commercial level,

no, it's not gonna happen.

Well it did, and gangbusters

and unfortunately

despite all the

implementation of biosecurity

protocols, I hate to say it,

but it probably will happen

again, albeit, I hope not.

It's not good for anybody, including the animals involved.

And so those of you

who do keep chickens

or who are involved

in educating yourself

about the usefulness

of genetic diversity,

I certainly hope that

you can see that chickens

are much more than

maybe, Sunday dinner,

or a source of eggs.

The evolutionary importance

in terms of research,

birds are models for a

lot of human diseases

like fetal alcohol syndrome,

speech impediment learning,

vocal communication,

things like that,

bone morphogenesis, chickens are one of the greatest models.

We also have a connection

to human culture as well

and so chickens are

important facets.

We have no time, I'm

over time, my apologies.

But there's just

so much cool stuff,

particularly in the

cultural aspects,

namely the religious

importance of chickens.

In Vietnam, often on

Catholic churches,

you'll actually see a

weather vane of a rooster

and I've noticed that

some older North American

towns, you can see that

on many churches as well.

There's none around

here, but I know

over in Michigan, I've

seen a number of them,

one near Hope College, in fact.

But the point here

is, we have the tools

available to conserve

our genetic resources,

to conserve our

agricultural animals

and also the natural

biodiversity.

We can't sit aside

and let it go by.

It's just too valuable

and too important

for the evolution

of our own future.

So, thanks so much

for attending.

[audience applauding]

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