How did early humans take on racial characteristics now seen today across the world?

[Xanikk999]

I started thinking about this just a couple of minutes ago. Early humans like homo erectus and homo habilis in all my biology book were shown as white human beings.

I find this very ironic since homo erectus i beileve was the first human species to migrate out of africa to other parts of the world. And meanwhile it says in various sources that humans crossed the land bridge to north america only a couple 10,000 years ago.

This begs the question how long did it take for humans to look like the different races we have today? Native americans look very different then any other human race. So maybe evolution in slight bits have been occuring on a much more recent scale. I do know that all human races are the same species but they look vastly different.

What do you think?

 

[skadistic]

Saw a special on this where they tracked genetics. All race based mutations are mostly because of enviriomental factors such as UV levels and inbreading. The genetic tests showed that Persia is the center of the races for the most part. How long its taken to mutate a diffrent race is dependant on not time but isolation too.

 

[ketalis]

Environmental factors such as variations in nutrient intake and climate. For instance, the diet of your average Japanese person has changed quite a bit in the past fifty years and the average height has been rising in conjunction. It's ridiculous to think the first homo sapiens were white, IMO. They were definately blacks originating from Africa. What caused the paleness? Living in cold climates forced us to live in caves so that we saw far less sun than our plain-dwelling comrades. It would seem that the native Americans went from being black (in Africa) to being white (cavedwellers) and were back on the path of heading to blackness by living in the sun. However, they had only progressed so far as to be reddish. *shrugs*

 

[Xanikk999]

Environmental factors such as variations in nutrient intake and climate. For instance, the diet of your average Japanese person has changed quite a bit in the past fifty years and the average height has been rising in conjunction. It's ridiculous to think the first homo sapiens were white, IMO. They were definately blacks originating from Africa. What caused the paleness? Living in cold climates forced us to live in caves so that we saw far less sun than our plain-dwelling comrades. It would seem that the native Americans went from being black (in Africa) to being white (cavedwellers) and were back on the path of heading to blackness by living in the sun. However, they had only progressed so far as to be reddish. *shrugs*

But evolution has nothing to do with changes in the enviroment that happen during a persons life.

Change is based on completely random mutations that are passed on through succesful offspring.

 

[GenMarshall]

I find that it has to be genetic mutations based on which lattitdude the early humans were living at. If they lived closer to the equater, then they would have a darker skin tone. If they live closer to the poles or in regions where it does not recive that much sunlight, they would have a much lighter skin.

 

[Xanikk999]

Environmental factors such as variations in nutrient intake and climate. For instance, the diet of your average Japanese person has changed quite a bit in the past fifty years and the average height has been rising in conjunction. It's ridiculous to think the first homo sapiens were white, IMO. They were definately blacks originating from Africa. What caused the paleness? Living in cold climates forced us to live in caves so that we saw far less sun than our plain-dwelling comrades. It would seem that the native Americans went from being black (in Africa) to being white (cavedwellers) and were back on the path of heading to blackness by living in the sun. However, they had only progressed so far as to be reddish. *shrugs*

Double post sorry first time also

 

[Xanikk999]

Anyway i always thought change that occurs within a species is the result of completely random mutations that have nothing to do with outside factors. And if the bearers of those mutations wether benificial or not survive then eventually all the random mutations will create a new species or the species will look different.

Notice im no biology expert but i read it alot.

 

[CartesianFart]

Environmental factors such as variations in nutrient intake and climate. For instance, the diet of your average Japanese person has changed quite a bit in the past fifty years and the average height has been rising in conjunction. It's ridiculous to think the first homo sapiens were white, IMO. They were definately blacks originating from Africa. What caused the paleness? Living in cold climates forced us to live in caves so that we saw far less sun than our plain-dwelling comrades. It would seem that the native Americans went from being black (in Africa) to being white (cavedwellers) and were back on the path of heading to blackness by living in the sun. However, they had only progressed so far as to be reddish. *shrugs*

I guess so.I already got an idea what the Indians(not the native american of course)are all about.They are actually europeans that was left stranded in India during the migration and was burnt to crisp(somewhat a pasty white guy that was under the Sun for about 5,000 years)and that is why their color seems somewhat overtanned.

 

[ketalis]

But evolution has nothing to do with changes in the enviroment that happen during a persons life.

Change is based on completely random mutations that are passed on through succesful offspring.

Well then I just don't get it because I don't see how being paler would help anyone survive better at all. Perhaps a group of highly fit albinos that inbred?

Well Cartesian what's your explanation for skin color variations if not UV.

 

[SeleucusNicator]

iirc, a few weeks ago there was a study which essentially said that the change in skin color can be traced to two mutations, one which led to the white skin of caucasians, and one which led to the skin color in Asians.

It would seem to me that some racial traits, like skin color, would spread because they would be beneficial to the region in which they occur, and indeed be selected against in regions in which tehy do not occur. Others, like nose shape, would be neither advantagous nor disadvantagous, and would spread because, well, people living together breed with each other, and its easy for a random mutation like that to become quite common.

Races and their unique characteristics are the result of a population breeding within itself, essentially. Or at least that's what I've concluded without looking at the actual genetic evidence. It's what would make sense to me initially.

 

[SeleucusNicator]

Well then I just don't get it because I don't see how being paler would help anyone survive better at all.

In higher lattitudes, you get less sunlight and being pale protects you from Vitamin D deficiency. In lower lattitudes, being pale means you die of skin cancer rather quickly.

 

[skadistic]

But evolution has nothing to do with changes in the enviroment that happen during a persons life.

Change is based on completely random mutations that are passed on through succesful offspring.

Not all mutations are random. Some like skin colour are results of enviromental conditions. Think of it like tanning. More sun exposure = darker skin. In a cold nothern climate where the days are shorter and people wore clothing less UV bombarded the skin so the body didn't have to make as much melontonin (SP?). This would be a learned mutation.

 

[SeleucusNicator]

Not all mutations are random. Some like skin colour are results of enviromental conditions. Think of it like tanning. More sun exposure = darker skin. In a cold nothern climate where the days are shorter and people wore clothing less UV bombarded the skin so the body didn't have to make as much melontonin (SP?). This would be a learned mutation.

This in and of itself would not result in selection in favor of pale skin in northern lattitudes. There would have to be some benefit in having lighter skin or some disadvantage in having darker skin.

 

[Xanikk999]

But if its a learned mutation like in that case it wouldnt pass on to your kids. Thus it would not be evolutionary or anything.

 

[shadow2k]

I started thinking about this just a couple of minutes ago. Early humans like homo erectus and homo habilis in all my biology book were shown as white human beings.

I find this very ironic since homo erectus i beileve was the first human species to migrate out of africa to other parts of the world. And meanwhile it says in various sources that humans crossed the land bridge to north america only a couple 10,000 years ago.

This begs the question how long did it take for humans to look like the different races we have today? Native americans look very different then any other human race. So maybe evolution in slight bits have been occuring on a much more recent scale. I do know that all human races are the same species but they look vastly different.

What do you think?

Let's just say, for argument's sake, that they crossed the land bridge to North America around 10,000yrs ago. Are you wondering about Native Americans then? They were sort of an inbetween, color, neither black nor white. They certainly didn't run straight from Africa all the way to N.America in a single hike. It took a lot of time. Estimations vary on when and how humans started to leave Africa, but it most likely happened in waves, and there's no telling when they left, or how long they were out before they got to where they ended up. Keep in mind that diet can also alter skin color, check out the Inuit...dark skinned near the N.Pole, partly because of what they eat.

I really don't think N.Americans looked all that different. They had some partial traits of a lot of different people if you look at it closely enough.

From what I've read, it would take around 20,000yrs for black > white or vice versa. Or maybe I heard it in a lecture, I can't remember.

As far as science books...remember, we learn new things every day. Some books still show the evolution step-ladder that implies that we went from monkey to man (or whatever it might show). In reality, it should show a tree branch where a lot of what would have been the transitional species die off, and only one branch makes it all the way to you and I.

The "pictures" of the early humans are best guesses, but...early humans could have been white...just depends on exactly how and when they got to where they were.

This is just from wiki by the way, there are plenty of other articles plastered all over the net about skin color evolution though.

Human skin color can range from almost black to nearly colorless (appearing pinkish white due to the blood in the skin) in different people. In general, people with ancestors from sunny regions have darker skin than people with ancestors from regions with less sunlight. However, this is complicated by the fact that there are people whose ancestors come from both sunny and less-sunny regions; and these people may have skin colors across the spectrum. On average, women have slightly lighter skin than men. On a cultural level, color metaphors for race have evolved based upon genetic variations in human skin color.

Skin color is determined by the amount and type of the pigment melanin in the skin. Melanin comes in two types: pheomelanin (red to yellow) and eumelanin (dark brown to black). Both amount and type are determined by four to six genes which operate under incomplete dominance. One copy of each of those genes is inherited from the father and one from the mother. Each gene comes in several alleles, resulting in a great variety of different skin colors.

Dark skin protects against skin cancer caused by mutations in skin cells induced by ultraviolet light. Light-skinned persons have about a tenfold greater risk of dying from skin cancer under equal sun conditions. Furthermore, dark skin prevents UV-A radiation from destroying the essential B vitamin folate. Folate is needed for the synthesis of DNA in dividing cells and too low levels of folate in pregnant women are associated with birth defects.

While dark skin protects vitamin B, it can lead to a vitamin D deficiency. The advantage of light skin is that it lets more sunlight through, which leads to increased production of vitamin D3, necessary for calcium absorption and bone growth. The lighter skin of women may result from the higher calcium needs of women during pregnancy and lactation.

The evolution of the different skin colors is thought to have occurred as follows: the haired ancestors of humans, like modern great apes, had light skin under their hair. Once the hair was lost, they evolved dark skin, needed to prevent low folate levels since they lived in sun-rich Africa. (The skin cancer connection is probably of secondary importance, since skin cancer usually kills only after the reproductive age and therefore doesn't exert much evolutionary pressure.) When humans migrated to sun-poorer regions in the north, low vitamin D3 levels became a problem and light skin color evolved.

Dark-skinned people who live in sun-poor regions often lack vitamin D3, one reason for the fortification of milk with vitamin D in some countries.

The Inuit are a special case: even though they live in an extremely sun-poor environment, they have retained their relatively dark skin. This can be explained by the fact that their traditional animal-based diet provides plenty of vitamin D.

Albinism is a condition characterized by the absence of melanin, resulting in white skin and hair; it is caused by a genetic mutation.

Skin color has sometimes been used in an (often controversial) attempt to define human races; see also racism.

 

[Neonanocyborgasm]

I started thinking about this just a couple of minutes ago. Early humans like homo erectus and homo habilis in all my biology book were shown as white human beings.

I find this very ironic since homo erectus i beileve was the first human species to migrate out of africa to other parts of the world. And meanwhile it says in various sources that humans crossed the land bridge to north america only a couple 10,000 years ago.

This begs the question how long did it take for humans to look like the different races we have today? Native americans look very different then any other human race. So maybe evolution in slight bits have been occuring on a much more recent scale. I do know that all human races are the same species but they look vastly different.

What do you think?

The skin color adaptation is based on Vitamin D production. Humans produce Vitamin D from UV sunlight on exposed skin. The light triggers a reaction that allowed cholesterol to be converted to Vitamin D (actually, there's a process in the liver and kidney that sequentially activates further function). Dark skin requires longer sunlight exposure to generate enough Vitamin D for survival. In more northern latitudes, days are shorter in winter so there are times when sunlight exposure falls dangerously close to critical levels. This is probably why people of more northern ancestry evolved into lighter skin.

The time in which these changes took was probably short, perhaps as little as 10-20,000 years.

 

[Cuivienen]

In Africa, nature prefers darker skin. Because of the heavy exposure to direct sunlight, darker skin tones allow for greater protection against ultraviolet radiation and debilitating sunburns. Sunburns would have been a major problem before civilization when a sunburned human would have been a drag on their tribe because they could not forage and would develop "sun-fever." Thus, humans with darker skin were more likely to reproduce in high-sunlight environments such as Africa.

In Europe, nature prefers lighter skin. Because of the minimal exposure to direct sunlight, lighter skin tones allow for greater production of Vitamin D as they do not block as much incoming radiation needed for Vitamin D production. A Vitamin D deficiency can be extremely debilitating, so humans with darker skin would not have reproduced as often. (Today, you can stay in all of the time because many things you drink, especially milk, are fortified with Vitamin D.)

In Asia, particularly in eastern Asia, skin tone was not as major an issue - middling skin tones developed for reasons above. However, the major racial difference, the extra flap of skin above the eye, developed also as a result of the environment. In the Asian steppes, where the East Asian race evolved, there is a great deal more blowing sand and dust than in Africa (outside of the deserts) and Europe. The extra flap of skin prevented dust and sand from becoming lodged above the eye, preventing eventual blindness caused by the constant grinding action of the particles. Therefore, hummans with this extra flap were more likely to reproduce.

Of course, all of the genes for these adaptations were present in the early human population before migration from Africa, albeit in small numbers. Once a trait became useful, it began to proliferate, eventually dominating a region. It is very likely that all early humans with, for example, blonde hair moved to two places - northern Europe and Australia - as those are the only two places where blonde hair exists today, but the most parsimonious conclusion about blonde hair evolution is that it appeared in an early population that contained both ancestors of Aborigines and Europeans. At one point it was probably a very rare trait, but in a small population it became common due to the Bottleneck Effect. (Yes, Aborigines have a high rate of blonde hair.)

 

[Shaihulud]

My theorty is that all racial characteristics such as colouring, physical morphology are because human beings are such an inbred species. Scientific research shows that species that breed closely within the family shows marked colourings and body shape from the original, and human beings have a very low genetic variablity, such that it was theorised that the present human beings are propably descended from as population of about a few thousand individuals not too long ago. Ofcourse the enviroment accentuates some of the physical appearance, but 10,000yrs is really short to make such a big chage.

 

[bad_ronald]

Not all mutations are random. Some like skin colour are results of enviromental conditions. Think of it like tanning. More sun exposure = darker skin. In a cold nothern climate where the days are shorter and people wore clothing less UV bombarded the skin so the body didn't have to make as much melontonin (SP?). This would be a learned mutation.

You're confusing mutation with evolution. The mutations in the germline that cause the amount of melanin in a person's skin to change are random. It's selective pressure in favor of lighter or darker skin that provides direction.

But if its a learned mutation like in that case it wouldnt pass on to your kids. Thus it would not be evolutionary or anything.

Then, just how do you explain the high heritability of the amount of melanin in the skin (i.e., it is indeed passed along to a person's descendants)?

Of course, all of the genes for these adaptations were present in the early human population before migration from Africa, albeit in small numbers.

What is so special about the stage of human evolution before the migrations out of Africa that uniquely allowed (beneficial) mutations? What has changed since to prevent novel mutations?

It is very likely that all early humans with, for example, blonde hair moved to two places - northern Europe and Australia - as those are the only two places where blond hair exists today...

It's much more likely that blondism evolved separately in Europeans and Australian aboriginals. [continued below]

...but the most parsimonious conclusion about blonde hair evolution is that it appeared in an early population that contained both ancestors of Aborigines and Europeans.

This is especially unlikely. If one founder group is responsible for blondism in both Europeans and Australian Aboriginals, they should have given each group the relative allele frequencies that represent this group's accumulated mutations. This would predict that Europeans are more similar to Australian aboriginals than any other group, which contradicts the findings on the clinal nature of the distribution of most measured genetically based phenotypes.

 

[vikingruler]

My theory on the Native Americans is that they started with original mankind in Africa or wherever they were but they needed darker skin to block the high sun exposure. As they crossed the land bridge to America they got lighter and lighter, people lived on that land bridge before they got America. There skin color had to have gotten lighter due to their distance from the equator. They arrive in america and their skin color becomes reddish the color of sun burns. Since they went so long without massive sun pressure the new sun exposure gave them that permament sun burn type color.

Gradualism and punctuated equilibrium are as far as I know the two main evolutinary theories. Gradualism is the slow change over time but PE is a step like evolution caused by rapid mutation of a few cells. Along with natural selection things like the extra flap of skin and East Asians would occur allowing these racial characteristics to occur. Natural selection allows two East Asians who have that extra flap of skin to give birth a child who has that flap of skin. PE lets people quickly adapt to their enviroments, i.e. black people adapt to cold climates like the land bridge.