Biology Human Evolution

Welcome back to www.educator.com, this is the lesson on human evolution.0000

Before we talk about the details of where we came from and why, with human evolution we got to talk about primates, that is our general group.0005

If you look at the taxonomy lesson, our order, the group of living beings that we belong to0013

based on similarities with looks, means, and such, we are primates.0019

Primates originally evolve from an arboreal tree dwelling mammal 85 to 60 million years ago.0025

There is some debate on exactly when, if you look at the fossil evidence0032

based on tree dwelling mammals that time, this is the range that is current.0037

That arboreal mammal would have had forelimbs, it would have had probably a slightly longer face than the average primate.0045

I have seen images of what they think it might have looked like.0054

It almost look like a tree shrew, but a lot of changes had to happen to the descendants of that particular mammal,0057

to get into what we now know as primates, monkeys, apes, us, in the like.0065

Typical primate characteristics, front facing eyes, like I just scratch my eye, it is in the front of my face.0071

Other animals, I’m sure you have noticed, some has their eyes on the side of their head like a bird.0079

A bird will move its head from side to side so it can a get a good view of everything around it.0085

The fact that we do not have eyes on the side of our head, but they are in front of our head gives binocular vision,0091

the fact that we have overlapping visual fields and we have a better sense of depth.0096

That is important for primates especially swinging through the trees.0101

Knowing exactly how far away that next branch is to catch or whatever, is very important.0104

That is the binocular vision also called stereoscopic vision.0112

Most primates have color vision, the ones that are night dwellers, the nocturnal ones, tend to not.0116

Color vision is very common in primates.0126

Opposable thumbs or toes, some have only one of them being opposable like us.0128

We have opposable thumbs, our big toes not opposable.0134

However, when you look at other primates, they can grab things with their feet as if it is a hand.0138

They will hang from a branch upside down which is much harder for a human to do.0144

Large brains, compared to other mammals, we have a bigger brain to body ratio, in terms of mass.0148

Upright posture is very common, the fact that you can see a lot of primates ambling around on just their hind legs0155

and not having to put pressure always on their front legs.0163

Fewer offspring and more dependency, meaning compared to other mammals,0168

other individuals in our class, the mammalian class, we have less babies per time we mate.0173

You get more dependency of the offspring on us.0183

There is a lot more maternal care that tends to happen with primates compared to other mammals and certainly other vertebrates.0186

These things, they may not all be true of an individual species of primates but these are typical characteristics.0194

There are two major groups within order primata or the order primates.0201

The Strepsirrhines, these are more ancient lineage of primates.0206

They looked almost like aliens, I’m not saying that they actually came from another planet.0211

The strepsirrhines includes the lemurs, lorises, aye-ayes, galagos.0216

I have some examples here, this particular individual here that is an aye-aye from Madagascar.0222

The aye-aye has a very long finger in each hand, they can dig in to get insects from trees, they are nocturnal.0230

The aye-aye is in the same group as lorises and lemurs.0238

Definitely not as closely related to us as other primates.0243

The tarsiers are used to be considered related to them.0247

It is actually in the group Haplorhines, which is our group.0252

Further evidence from the genetics of tarsiers has shown it is probably not as closely related to the aye-aye,0257

even though it looks like it should be.0264

This tarsier is also a nocturnal animal, you can see from its very large eyes.0267

It is kind of an interesting looking animal.0275

The Haplorhines also includes monkeys, apes like chimpanzees, and humans, and our closer relatives.0277

The Anthropoids is a subgroup within Haplorhines, and it basically includes all of these, monkeys, apes, and humans.0286

Basically, Anthropoids are all haplorhines except for tarsiers.0296

I’m going to focus more on the anthropoids, we are getting closer into the humans.0299

Anthropoids, slide number 1.0305

The anthropoids are group diverged from other primates about 35,000,000 years ago.0308

We are going to start with the monkeys.0312

New world monkeys, the ones you would find in central and south America.0314

Spider monkeys, howler monkeys, and more, I’m just giving you a few examples.0320

The spider monkey is right here, this is a spider monkey.0325

It gets its name because look at that, look at what it can do.0331

Its tail is like a 5th limb, it is prehensile.0336

That is actually very common, prehensile tails are very common in new world monkeys.0340

They do not all have them but it is very common for them to have a tail, it almost acts like another arm.0344

Howler monkeys, I have seen them in person in Costa Rica, they can howl, let me tell you.0350

Capuchin, you see them in a lot of movies and TV shows.0355

New world monkeys, the fact that monkeys exist in multiple continents shows you that,0359

this group came to be before the continents completely separated.0364

That is how you got them into different continents.0368

Once the continents separated, you have isolation of those different groups.0370

That is how you get the differences occurring because of those isolated populations.0372

Old world monkeys, Africa and Asia, this includes the melakas, baboons, colobus monkeys.0378

No prehensile tails, you just do not find them.0386

They tend to be larger as well, compared to new world monkeys.0389

Back to the tails, some of these monkeys do not even have a tail.0392

It is not common for monkeys to do not have tails, compared to apes.0397

Some definite differences when it comes to tails, comparing the old world and the new world.0401

Here is an example of a melaka monkey, just chilling.0405

Anthropoids number 2, you also have hominoids as a subgroup.0412

This would be the non-monkey anthropoids.0418

We just talked about the anthropoids that would not be hominoids.0421

This actually starts to sound more like our name, we are Homo sapiens.0426

Hominoids, that Homo, the root is the same, meaning same as us.0432

The lesser apes would include gibbons and siamangs.0438

Here we have one of those lesser apes, also just chilling.0442

The greater apes are gorillas, orangutans, chimpanzees, and bonobos.0448

This is a bonobo chimpanzee, this kind of chimpanzees also called the common chimpanzee,0451

used be called the pygmy chimpanzee.0458

Bonobos is a relative of chimpanzees that is the closest to us, in terms of resembling us and acting like us.0460

Hominins, finally we get into a smaller group within hominoids.0470

This would be the hominoids that are not apes.0476

This is us, and all of our relatives that are much closer to us, in terms of genetics and ancestry, than chimps and their ancestors.0480

This is humans and their extinct relatives.0491

Our group, hominins split off from other African apes 8 to 5,000,000 years ago.0494

More fossil evidence in the future will allow us to pinpoint this more precisely.0500

This is used to be called Hominids, this N in older textbooks used to be a D.0505

Hominins is now the more acceptable term.0513

When I took this in high school, the term in the textbooks was hominids.0515

If you see that in other research related to this, hominids and Homonins are basically the same.0520

What is the deal, how they are special among primates?0528

Larger brains than other hominoids, when you look at the brain mass to body mass ratio,0532

definitely more in favor of the larger brains.0539

Thinner, flatter face with smaller teeth, in a lot of monkeys and apes you see very large teeth.0542

Our teeth size reduced, we still have teeth that are specialized for an omnivorous diet.0549

Omnivores meaning we eat animal and plant material, omni meaning all.0556

We have sharp teeth and flatter teeth for grinding.0566

Higher manual dexterity, which makes sense that us, in our relatives, are better able to move our digits more precisely.0569

It allows us to have tool making and other things like that.0578

All hominins are bipedal.0581

Bipedal as opposed to quadrupedal.0584

Bipedal is walking on two legs, not having to put any weight on our front legs.0588

Quadrupedal is on four.0593

You might think, I have seen gorillas and chimps walk around on their hind legs.0597

They are not entirely bipedal because when they run really fast, they end up putting weight on their front limbs, both of them do.0602

If you observe them for long enough, you will see it.0610

Yes, they can sit there and walk briefly on their hind legs.0613

Unless you are look at a crawling human in infant or toddler, you are not going to see quadrupedals in us as the norm.0618

Why did bipedal is not developed?0626

There are few theories, I will just touch a couple of them.0628

There is the savannah hypothesis, tells us that there may have been an environmental change0631

to that geographic region of Africa to the point where a lot of the trees went away.0649

Maybe it was drought, temperature change, but not having any trees like swing around through from tree to tree,0656

puts pressure on you to get down from the tree and walk distances, and be more exposed on the ground.0663

Also, they are advantages of being on two legs.0670

You can be higher, you can be taller, and look over things, to look more on the distance of predators if you are on the ground.0672

Also, you can grab things, we are talking grab and hold things while traveling, while running or walking.0678

That can be very useful, you can imagine the advantages of doing that.0689

All Homonins are bipedal, and the other currently existing primates other than us are quadrupedal.0694

This is an interesting little history of where we came from.0701

It does start before this but about 2 million years ago, you see home ergaster, erectus, etc.0706

Here we are, they show where on Earth you find these specimens, where you find fossils, or in our case modern day individuals.0714

Yes, this is our lineage here.0724

It is an interesting image.0727

Australopithecines, this is a group that does not include us.0733

It is hominins but it is Homonins that are a little bit more in the past, a little bit more distant.0737

The earliest fossil evidence for being on two legs is about 6 million years old.0743

MYA will always stand for in this lesson, millions of years ago, MYA.0749

I have actually seen an image of fossilized footprints that show all the weight being put on the feet and none on the hands.0766

From definitely more than 3 million years ago, closer to 4 million years ago.0776

Evidence has suggested that it is far back as about 6, which is impressive.0781

Early Australopithecines, in terms of fossil evidence about 4.2 million years ago, as far as the radioactive dating.0786

Australopithecines means southern ape.0796

It is somewhat of a misnomer because when they were named, the categorization and understanding what an ape is, was more in its infancy.0798

They are not actually apes, they are in our group, they are much more closely related to us, more humanlike for certain.0807

The most famous fossil find from this group of Australopithecines is Lucy.0814

Here is her scientific name, Australopithecines afarensis.0818

Afar means that she was discovered in the Afar valley in Kenya in 1974.0823

She is one of the more famous ones because this is actually an image of the fossils from her, all from one individual.0831

That is a lot of fossils, I rarely do find all of these from an individual that is 3-4 million years old, that is really rare.0839

Based on this discovery, we know that she had a small brain compared to modern day humans.0851

But walked upright, based on the way around the bones, analyzing those, we know that she was not running around like a gorilla or chimp.0856

More curvature to her finger bones as well, which is interesting to think0866

because we are pretty certain because of the extra curvature,0870

that she was still used to like occasionally being dependent on trees, swinging from branch to branch.0873

But, probably came down from the trees to scavenge for food, maybe run from tree to tree.0879

She has to come down from the branches but probably slept in the trees still.0886

She would have been much smaller, height wise, definitely hairy.0890

This is an image, an artist's conception, a sculpture made related to the bone structure of which she probably look like.0897

You are getting this more mosaic pattern of like ape characteristics mixed with human characteristics.0905

A transitional form getting closer and closer to what we see as a modern day human in the Australopithecines.0912

The Australopithecines existed for millions of years and then you get this new group, our genus, where the scientific name begins with Homo.0922

The genus Homo meaning same.0930

By one million years ago, all the Australopithecines disappear from the fossil record.0933

Maybe in the future, we may discover of an 800,000 year old Australopithecines.0937

It does not look likely at this point but you will never know, that knowledge can change over time.0943

Here is an example of fossil hominids.0948

Like I mentioned before, there is that D hominid.0951

Now we tend to see hominins.0955

Back in time, you could see the lower ones here, these are the older fossils.0957

As you get further and further up, they get closer to us, modern day humans.0962

But, you get some weird things off in the side.0967

Like this one here, Australopithecines boisei or paranthropus boisei is another genus.0971

It is one of those tangents off to the side before it getting to this Homo genus that has a dead.0978

We do not think that they were many descendants after it, as far as we can tell.0983

Human evolution is not a single line, like that lineup where you see like a hunched over and0989

you get to the cave men guy and than us.0995

It is not a single line, it is definitely a tree, some of the branches end, some keep going.0999

The genus Homo includes living and extinct humans.1005

All the way back to Homo habilis, we will get to habilis, next.1008

Bigger brains compared to the earlier forms, lighter skeletons, flatter faces,1012

you do not get as much the jaw or muscle coming out.1017

Smaller teeth, not as much of the fang look, even more reduced.1022

Tool use, this is really important, you finally see legitimate tools.1030

If Lucy used tools, they would have been found objects, throwing a rock, picking up a bone and smashing something with a bone.1035

We do not believe that her species had the capacity or ability to make actual formed tools.1044

But, the brain and body ratio of genus Homo, these Hominins, yes.1052

Homo habilis, actually even though this is the title of the slide, I just want to make note of this that,1060

when you actually write the scientific name, the second name, the species name is typically lower case.1072

Just in terms of scientific notation, I just want you to understand that1080

I did not make that mistake in this particular lesson that the title of the slides are all going to be capitalized.1086

If you would to be tested on whether or not you wrote almost Homo sapiens correctly, you would actually write it out like this.1091

If you are handwriting it, you underline it.1101

You would italicize it, if you are actually typing it.1103

More on than, if you a look at the taxonomy lesson about classifying organisms.1107

Homo habilis, some people say habilis.1114

Homo habilis existed about 2.4 to 1.4 million years ago.1117

The cranium size, meaning the actual size of this casing in here that holds the brain, the volume of it is 650 cc,1123

that is 20% larger than Australopithecines, than something like Lucy.1132

If you are wondering, how does this relate to home sapiens brain size, that is close to half.1138

Yes, because we are about 1350.1145

It would have been shorter, do not think that they were dumb, less intellectual ability but they definitely made tools.1148

The name means handy human or handyman because it is the first to be found with stone tools like legitimate,1157

like here is a remnant of a tool that this is not something that exists in nature, they modeled it,1164

they fashion it, for the sake of making life easier.1169

It is only found in Africa, telling us that the Homo habilis did not migrate out of Africa.1174

It migrated around Africa but did not leave.1181

Probably still dependent partially on trees, as far as we can tell.1184

We do not think they made structures like made shelter.1189

If they are in Africa for safety purposes, being on trees especially when they are sleeping probably would have been advantageous.1194

This is an artist depiction of what a Homo habilis individual may have look like.1202

Here is a remnant of fossilized skull from Homo habilis.1206

Homo ergaster, 1.8 to 1.2 million years old, this is a little bit later.1212

The cranium size 1000 cc, that is a big spike compared to 650 from before.1218

It is taller and lighter than Homo habilis, the previous one.1225

It had a human like nose, they say that it is the first humanlike noses in the fossil record of Hominins.1229

The nostrils tend to be pointing downwards rather than up and out.1237

Found in and outside of Africa, extensive migration, not just found in Africa, found in other regions.1242

Definitely, it got around, maybe it was following its food.1249

If it was dependent on certain food sources that migrated because of vegetation changes, this group would have followed.1254

Tools showed that it most likely hunted, but there were some debate.1262

Some scientists believe it was still scavenger, this species would have still just kind of found food instead of hunting it.1265

They made some legitimate tools, fashioned tools that could have been used to kill animals.1275

That is why a lot of scientists think this might have been the first, like real hunter, almost 2 million years ago.1282

Home erectus is somewhat misnamed because when it was discovered way back in the late 1800,1293

scientist thought it was upright.1301

This is our upright ancestor, maybe the first one that stood up.1305

They were plenty that came before this, including Lucy, 2 million years prior that would have already been upright.1309

The name is not perfect for this but it is what it is.1317

1.8 million years ago to 400 thousand years ago, that is what 0.4 million years would be.1324

That is amazing, it lived nearly 1½ million years.1330

Our species has only been around about 200,000 years, we have not got that far yet.1336

Cranium is very similar to ergaster.1341

Some scientists consider the same species as ergaster.1353

Others say that ergaster found in different areas slight differences in the skeleton.1357

Some scientists think that ergasters is just an earlier form of erectus, it is up for debate.1362

The name of home erectus means upright human like I suggested.1368

Found in Africa, Asia, and Europe, definitely migrated extensively.1372

Thinner skull bones but larger brow, you can see that the brow still sticks out a bit in this particular species but humanlike teeth.1376

It used fire, there is evidence in the same strata, the same region where these fossils1386

have been discovered that there is charred animal bones.1394

It does not tell us that animals spontaneously combusted around them, no.1398

If there are charred animal bones found in a lot of different sites where these fossils are,1404

that tells us that they cooked the animals and that is the reason why animal bones would be charred.1409

They also definitely made tools just like the previous species.1416

Mastering fire, that is a big step.1422

Homo heidelbergensis was originally found in the Heidelberg region 1.3 million years ago to 0.2 million years ago.1427

Cranium size a bit bigger and you can see that it even exceeded humans, just a little bit 1100 to 1400.1439

Human’s average size is 1350.1448

That does not mean that they were smarter than us.1451

It could be that their brain connections might have been a little bit different from ours, as far as we know.1454

This is a transitional form between Homo erectus and Homo sapiens.1461

A lot of scientists consider Homo heidelbergensis to be just a very early form of Homo sapiens.1464

You are getting definitely really close to the look of a human skull.1471

Larger brains and finger bones, than Homo erectus.1476

Still not prominent brow, the chin which you cannot see here because thee is no mandible.1480

The chin is not as prominent, it is definitely receding, getting a little smaller.1485

That is Homo heidelbergensis, found in multiple regions as well.1492

Homo sapiens neanderthalensis, traditionally these are called Neanderthals.1498

Some scientists I actually heard them call Neanderthal.1507

Regardless of how you spell it, that is the term Neanderthal.1513

Originally discovered in the Neander valley, that is why.1517

About 300,000 to 200 thousand years ago or 0.3 – 0.2 million years ago.1522

The cranium is bigger than ours.1527

It is originally discovered in the Neander valley like I mentioned, and found in Europe and Asia, exclusively.1530

This had not been discovered in Africa.1535

This is an offshoot from Homo erectus.1537

As far as we know, Homo erectus, a group of them gradually became us, and also became Neanderthals.1540

We have home erectus in common, as an ancestor.1560

There is evidence that interbreeding occurs.1565

Interbreeding with our species home sapiens sapiens will be the full name, occurred.1568

Here is how we know that.1574

There had been Neanderthals specimens completely frozen in ice.1576

We are not talking just fossils, we are talking about their whole bodies.1580

Since they are not that old compared to other ancestors, these cousins of ours, in a sense,1582

have been discovered intact which means it is easy to get the DNA out of them.1590

We have sequenced the vast majority of the Neanderthal genome.1595

You can look at all humans, all different groups of humans around the world,1600

and compare their genomes to the Neanderthal genome.1604

The amazing thing is that, every single human on earth has more in common with each other1606

than any of us do to a Neanderthal, which is a sign that we are all the same species.1612

However, there is also evidence that some humans have Neanderthal genes in them,1617

a certain percentage, a fairly small percentage.1623

Many people who have European descent have Neanderthal genes1627

which means that their ancestors mated with a Neanderthal and they had a hybrid offspring.1630

That did happen which means we are close enough in genetics and chromosome number, etc, to make offspring.1636

For some reason the Neanderthals died off.1645

They have theories about why, there is no proof either way.1647

There are theories that it could have been genocide by us.1650

It could have been viruses, it could have been their lack of adjusting to the environmental change.1654

Maybe they are more stubborn by how they did things, with the environmental change, they did not last.1662

It is hard to say exactly why.1667

They constructed complex structures like shelter and tools.1669

They had a language, I mean if their cranium size is similar to ours and they were social, they had a language.1674

They bury their dead.1680

Here is a diorama, like a little tiny clay representation of a Neanderthal settlement.1682

You could see that there is a dead body that they are burying.1690

It is very human like in how they interact with each other, you can see that.1694

The clothes that they done to probably to cover up their genitals in the exhibit.1698

Neanderthals would have worn clothes if it was cold, if the environment oriented the need to wear animal hides.1706

If it was really hot out, maybe clothes were not part of their custom.1716

Certainly, since a lot of the Neanderthals were discovered in Europe and Asia where it does get much colder,1720

wearing animal hides would have been advantageous.1727

Here is a comparison of a modern human and Neanderthal skull.1731

This is a Neanderthal, this is us.1734

You could see there are little bit differences here.1738

You got the kind of pointed bun, they call it, in the occipital region.1741

Forehead is a bit different, ours is a little bit more prominent of a forehead.1746

Their brow ridge a little bit more bumpy, a little bit more prominent.1751

Nasal bone projections are similar.1755

This one tends to come out a little bit more dramatically.1757

The angulations of the cheekbone, the chin, there are plenty of similarities.1760

You could tell that this skull is a bit more massive, slightly bigger brain but does not mean that they used to be better than us.1766

Homo sapiens sapiens, 195,000 years ago was the earliest human fossils that has ever been discovered.1775

And of course, we exist until the present.1782

Average cranium size 1350 cc.1785

Humans, early us, most likely evolved ones in Ethiopia, what is now Ethiopia, and migrated to all parts of the earth from there.1790

It is less likely that humans popped up in two different places and1800

just coincidentally just had genetics so close that, we are the same species.1803

The best theory is the out of Africa hypothesis that 195,000 years ago, what is now Ethiopia,1811

a small group of what once was Homo erectus is Homo sapiens sapiens, and spread all over the continents from there.1818

No brow ridge, we do not have that significant ridge that Neanderthals and the previous ones have.1826

Pretty small chin, there are obvious other differences.1831

You can look in the mirror and see them.1834

Creativity and more control over the environment is classic us.1837

Creativity, that expression, and more control over the environment.1841

Artistic expression, cave paintings, you really see that with early humans.1848

Sometimes they call them cromagnon humans.1853

Cave paintings, they need to express themselves, definitely unique to us.1857

Tailored clothing, not just like taking off animal hide and wrap it around myself, like actual made clothing.1862

Domesticated animals, you finally start to see that tens of thousands of years ago.1872

They hunt together, the combination of hunting for animals and gathering other nutrition combined together,1876

leads us to modern day society eventually.1886

Here is a skull from an earlier human, looks very similar to ours, of course.1889

Finally, Homo floresiensis is about 18,000 years old.1898

There is a span of time greater than that but most the specimens found around that time.1902

I went to Flores, I already discussed this in the evolution lesson but a quick review.1908

We think that a group of Homo erectus, by boat, got to the island of Flores within Indonesia.1914

That isolation of that group overtime lead to them being really small in stature.1921

They are also known as the hobbit species.1926

1 meter tall as adults, just about 3 feet tall, a little over 3 feet tall.1928

Their brain and body proportions are similar to actually Lucy's group, but stone tools found.1935

It is interesting that their brain size would have been smaller than expected for the tools that they did make.1942

Probably, earlier knowledge from their Homo erectus ancestors had them with the ability to retain tools,1949

even in an isolated spot on the island of Flores.1959

They are now all extinct, we did not know what happened to them but the human evolution story continues.1963

Now that we have gone over the species of different Hominins that have existed over millions of years,1970

what actually happened with humans that got us to be widespread all over the earth.1976

With home erectus and some other hominins, they did spread out but not as extensively as we have.1981

We have been around as long as some of the other Hominins, but we certainly have conquered the globe and spread quite a bit.1987

According to fossil evidence, humankind, what we know as Homo sapiens sapiens,1994

came to be in what is now Ethiopia around this area, central eastern Africa.1999

That was about 200,000 years ago.2005

I’m not going to give you exact thousands of years, in terms of when we ended up.2008

That is more of a historical thing, anthropological thing.2014

I want to talk about differences in terms of trends with phenotypes, different looks in appearances in different humans,2019

based on where they migrated as like an environmental explanation.2026

If this is where humans first ended up, according to fossil evidence.2032

There was initial spreading throughout Africa, over time.2036

Spreading from here all the way down to South Africa, it would have taken a long time.2041

It did not happen overnight.2046

It probably happened due to increased numbers of people, following their food source.2048

Because we are pretty sure they were hunter gathers, they depended on hunting particular animals.2054

And they did depend on plant life as well, as part of their diet.2060

When we look at people of African descent, central and southern Africa,2064

there tends to be a lot of phenotypic similarity, in terms of what they look like in general.2070

When we look at native peoples that descended here, after tens of thousands of years, they eventually ended up here.2076

Native peoples that eventually ended up here, one thing they do have in common is, since they are close to the equator2084

and they were there for a long time, they tend to have darker skin color, more melanation.2093

The reason for that is, there is sunlight, a lot of sunlight hitting the middle part of the year round.2100

In terms of seasonal change, it is not as dramatic as you get at the poles and that is because the tilt of the earth.2106

Up in the northern hemisphere during the winter, there is less sunlight.2113

When we look at the amount of sun hitting this part of the earth,2118

it makes sense that they would have had more development of melanin shielding them from a lot of that sunlight,2120

a lot of that UV radiation and making it less likely that they will get skin cancer.2125

I will tell you in a little bit how the opposite developed, in terms of people migrating of north over time.2130

Right here, you have the world's largest desert, the Sahara.2137

You can consider that a geographical barrier, resulting in some isolation.2147

Related to evolution, you are going to have people that migrated through here, probably along the Nile River, top here.2153

Related to evolution is, if you compare the average native north Africans,2161

someone that is from these parts from Egypt, Morocco, Libya, etc, in terms of phenotypic trends,2167

they tend to have more in common with people in this region, in terms of their look, in terms of average phenotypes.2176

Why, over time, there was probably less gene flow back and forth across the Sahara desert.2183

Having populations isolated more or so, and having these individuals a little bit farther away from the equator,2190

and having gene flow with these individuals, may have contributed to slight differences in their phenotypic look.2197

Extending this conversation further, people of Indian descent, people from Bangladesh, Afghanistan, and Pakistan,2204

have had more gene flow with each other, in terms of them settling here and2216

having people from those backgrounds interbreed, than across here.2220

Because right here, you have got the world's largest mountain and quite extensive mountain range, the Himalayan Mountains.2225

That is a geographical barrier from here over to other parts of Asia.2233

They tend to be phenotypic trends in these parts, in terms of the eye fold.2238

You are familiar with what I mean, people of Asian descent have a difference in their eye fold,2246

that probably originally resulted from a mutation.2252

Mutations have resulted in variety in all kinds of humans, whether we are talking about skin color differences,2255

hair differences, or the look around their eyes.2261

There are various explanations for why it is that developed,2265

did it have something to do with them settling up close to Siberia first and then descending down to these areas.2268

That is not entirely clear, some theories are more accepted than others.2274

In my opinion, that particular mutation is a dominant allele.2282

When you tend to have some of Asian descent and some Caucasians having a child,2288

the eye fold from the person of Asian descent tends to be dominant, in terms of that being expressed in the offspring.2293

That dominant mutation, all it would have taken was one person early on in this group to develop that.2301

Mating over time could have spread it throughout the species.2308

Whether or not it was actually something that gave them an advantage in the environment, that is debatable.2313

It could be that, early on in their travels, it could have been just considered attractive,2319

something that was different and unique and beautiful.2325

When you look at people who settled in Europe,2329

there is a trend in terms of skin color differences compared to people that is closer to the equator.2333

Why is that, if you look at the amount of sun hitting this area year round, there is less sun.2343

You have this opposite affect that gradually would have happen, in terms of less melanin production over time.2353

It did not happen overnight, it did not happen in 50 years, 100 years, it happened over thousands of years,2359

in terms of that gradual change phenotypically in these populations of humans up here.2363

It is especially true of northern Europeans because people who settled closer to here,2368

there was more gene flow with people from Africa.2375

Invading tribes came in here and change the bloodline occasionally.2377

That happened with a lot of different times in history.2382

The Mongolian empire extended all the way to Eastern Europe and over what is pre much all of Asia.2388

Genghis Khan and his hordes, they definitely altered the bloodline hundreds of years ago, in this part of the world as well.2395

When we look at people of European descent, in terms of melanin differences.2402

There have been studies with people who have very dark skin, let us say they are native Kenyan or from the Congo.2407

They settled up here in Norway or Sweden where there is a lot less light during certain parts of the year.2416

Some of them have to take vitamin D supplements because their dark skin color blocks a lot of the UV that is hitting them.2422

They are limited UV there, during certain times of the year.2428

Without that vitamin Di production in the skin that stimulated by UV, you can get some deficiencies.2431

Especially, if you are younger, vitamin D deficiencies would cause things like rickets, joint problems, bone problems.2438

The fact that people with naturally darker skin up here have to take a vitamin D supplement to stay healthy, oftentimes.2446

That is one of the pieces of evidence that as people settle up here, the lighter skin they had,2454

the more healthy they were as they went through life and settled here where there is less sunlight year round.2461

As I mentioned before, when you compare people of northern European descend to parts of Southern Europe,2468

you tend to see some darker features in people of from Spain and people from Italy, especially Sicily, Greece ,and Turkey.2473

Now Turkey is Asia minor, it is in between Europe and Asia.2482

Here you tend to have more gene flow with people that had some darker features, darker hairs, dark eyes.2487

If you look at my background, I’m a quarter Sicilian.2494

Certain people in my family who are a Sicilian descent, look much darker than I do.2495

They have dark hair, dark eyes, and slightly darker tone in their skin color.2502

That is because one of the many examples is the Moores, a tribe from North Africa invaded them and change the bloodline.2508

Like I said, it has happened numerous times throughout history.2517

If we look down here in Australia and New Zealand, most of the people there today look like me, they look Caucasians.2520

It is because this was Great Britain's territory for a long time.2527

The initial people who settled here were white, they were Caucasian.2535

Before that, the native peoples, way before European exploration,2539

you would have had the aboriginal groups and Mori tribes, that would have settled here from Southeast Asia.2545

They would have gradually made the way over here by boats and settled here.2553

Unfortunately, with exploration and conquering lands, they are not as many there today, as there were a long time ago.2559

When you look at the Philippines, the Philippines are a combination of native Pacific islander blood and Spanish blood.2568

Because back in the 1500’s Spain settled here, changed the bloodline.2577

It is happened a lot of times with gene flow, in terms of different populations of humans intermixing.2580

It has happened a lot in our history.2587

People who initially settled in the America, the theory is that they were tribes,2590

groups of people in Northern Asia that went across a land bridge, through what is now Alaska and Canada.2595

Perhaps, water level differences exposed a little bit of land between what is Eastern Russia or Eastern Asian continent and Alaska,2603

it could have been an ice bridge as well, that would have connected them.2616

Chances are they were following their food source.2619

Chances are they were following what they ate and what they depend on for their livelihood.2622

Over time, over thousands of years, they expanded all throughout these areas.2627

You have the native American tribes, people of Aztec, Mayan descent.2632

If you look back at the 14, 15, 1600’s, in terms of people from Europe settling here,2640

that is why there are a lot of people of Caucasian descent now in these areas.2649

People who speak Spanish, it is common for Mexico and Central America, these areas, to be speaking Spanish because those areas were settled by Spain.2654

The reason why Brazil, right around here, is Portuguese, is because of a long time ago, this random historical fact,2667

the pope who was in charge at the time, the pope have a lot of power over the various empires of Europe,2676

the different Kings and Queens, he made the line of demarcation.2682

He said that this line here, Portugal, you are heading to the east, Spain, you are heading through the west.2686

At that time, the map making was not quite as good, the exploration was not as good.2692

He thought he was giving it up pretty equally but Spain got a lot more out of the deal clearly,2696

because there is a lot more land over here, Spanish speaking nations.2701

Right here is Brazil.2704

There is a lot of gene flow here.2707

Unless if you are from Brazil, it would be probably hard for the average person2711

to distinguish somebody who is of Argentine descent with Brazilian descent, etc.,2713

Gene flow here between native groups that were once there first and still2719

there are people of those descent, people who consider themselves natives and have no white blood in them.2725

There is a lot of gene flow between Europeans who settled here and the native tribes.2733

A lot of people who settled in the Caribbean, and still today, you see a lot of individuals who looked of African descent.2738

It is because of the slave trade that they are brought over, same with the rest of the Americas.2748

Various countries took people from the African continent, they settled here, and they were slaves.2753

Now, thankfully they are free and can do as they wish, and go where they wish.2761

Because of some unfortunate circumstances in the history, people have been moved all around.2766

There has been a lot of gene flow between different populations and different looks,2773

and phenotypic trends, in terms of the human race.2776

Notice that every one of these groups that I have mentioned,2780

you cannot mention all of them in the time we have, I’m giving you a summary.2783

These groups, they are all still Homo sapiens sapiens, we are all the same species.2788

Why is that, a couple of reasons.2793

The amount of gene flow that is connecting those populations has kept us making offspring together.2796

Making biracial individuals, people of mixed race, it has happen quite a bit over time.2802

That gene flow has kept us the same species.2809

Also, there is no group of humans that has been isolated for a long enough time2811

and had enough unique mutations compared to everyone else, to be considered its own species that cannot interbreed.2816

Not enough time and not enough mutations have occurred for that to happen.2822

Now, if you do a get a group of people with no gene flow, no immigration and emigration in and out2826

for 200,000 years or more, they might have been being a unique species.2832

Whether or not they will have significant advantages to what we have, we do not know.2838

That is a brief summary of human migration related to phenotype, due to environmental differences and gene flow.2843

Thank you for watching www.educator.com.2850