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Anonymous asked in Science & MathematicsBiology · 1 year ago

If evolution is true, why are all humans the exact same species dispite being closed off and separated from others of the same species?

I understand the thery of evolution and natural selection to an extent. Dont get me wrong though, im a firm believer in evolution but i cant help but wonder this. If all living things adapt to different living conditions and climates just like how darwin observed the different adaptions of birds to their surroundings due to the birds being closed off from eachother and how we observe this same phenomenon through out the world and time.

Why did all "humans" evolve the exact same way (Evolve as in how previous classified evolutions of homo sapiens did not continue to live on and are found in different places throughout the globe) , dispite being totaly closed off from eachother? like how an untouched island tribe has the same genes as a modern person whos family has lived in the same place for as far as recorded time in a freezing climate and has no physical differences other than maybe skin color.

My reasoning for my question is very confusing and lacks proper recearch, but i hope you could provide me with awnsers and corrections.

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  • 1 year ago
    Favorite Answer

    It is certainly true that organisms adapt locally to their environments. That is why one population of the same species from one region may be different from another population in another region. Despite being different, they are the same species if they interbreed with each other when they meet. Whether such adaptations will result in the appearance of a brand new species depends on how different those different local environments are. If they are very different, then the hybrids between 2 different populations may not do well in either of these 2 environments. That in turn puts pressure on individuals of both species to avoid interbreeding since such mating will result in fewer offspring that will survive to adulthood and reproduce. When individuals from two populations of the same species refrain from interbreeding with each other because their hybrids are poorly equipped to survive and/or reproduce, then a new species has evolved because of adaptation to a different environment. Further, a new species can appear if different individuals within the same area adapt to different ways of living. This is known as sympatric speciation, and it is how new species can evolve in a lake or an ocean, even though 2 populations may not be isolated. Geographic isolation alone is often not enough to result in a new species forming, and often there is no need for geographic isolation for a new species to evolve. The main reason a new species evolves from an existing one is adaptation to a new niche, or way of life or a new environment.

    Humans evolved in Africa 150,000 years ago, and non-Africans evolved from a small group of Africans that migrated out of Africa. Many of the descendants of these migrants ended up in similar climates as Africa, and they still look very much like Africans even though genetically they are closer to Europeans and Mongoloids. These include the Australian aborigines, the Melanesians and the Negritoes (a minority in places like Thailand, Indonesia, Malaysia and the Philippines). Other non-Africans, such as the northern Chinese, Japanese, Koreans, and Europeans, have evolved adaptations to cold climates, such as lighter skin, straight hair, more facial and body hair, thin lips, taller and narrower nose bridges, shorter arms and legs, more subcutaneous fat, a rounder torso. Therefore there are more evolutionary changes than simply lighter skin.

    The reason these changes have not resulted in the appearance of a new species of humans is that despite these changes, humans still recognize each other as the same species and they interbreed freely through out history whenever people from different regions meet. A study of DNA for example shows that many people in SE Asian countries such as Thailand and Malaysia actually have Chinese ancestors in addition to dark skinned native ancestors. Indians have ancestors from various places, including Mongolians, Europeans and Central Asians, in addition to people who are close relatives to the Australian aborigines. People in the Middle East have European ancestors and also people who migrated out of Africa 60,000 years ago and never left the area. People continue to interbreed with each other because after the ice age has ended, the hybrids between cold-adapted people and those adapted to tropical climates no longer had difficulty surviving in any kind of weather. They simply wear more or less clothes to suit the weather. Because of the lack of a disadvantage for hybrids, people around the world, regardless of how different they may be, continue to interbreed freely, and that is why humans are still considered a single species.

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  • 1 year ago

    You missed the PBS special on the new info they have from Neanderthals, I take it. We interbred with them in the past, prior to 40,000 years ago. We have 4% Neanderthal genes in us, but not all of us have the SAME 4%, they've looked at our DNA and can reconstruct 75% of the Neanderthal DNA off it.

    Several other branches of human kind have died out due to changing environmental factors. That all happened in the past 100,000 years. Our branch came out of Africa and spread widely.

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  • Zirp
    Lv 7
    1 year ago

    Why we are the exact same RACE?

    The most plausible explanation is that we almost went extinct a couple of times. Just a few dozen millennia ago we were down to a few hundred, maybe a few thousand individuals. and some time before that

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  • MARK
    Lv 7
    1 year ago

    Your thesis is flawed from the outset. The isolation you claim has not occurred. Even if it had there has not been insufficient time for one population of humans to have evolved into another species.

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  • 1 year ago

    Population isolation has to be combined with randomly occurring genetic divergence AND differential selection due to unique environmental stresses in order to generate a new species. The first factor (population isolation) is a necessary but not sufficient factor. Your statement that it applies to most human populations is not consistent with the geo-archeaological evidence. Even populations such as Australian "aborigines" may not have been nearly as isolated as would be necessary to allow for genetic drift, and even if they were, there is still a need for a long time of isolation before chance events would be likely (not certain, but likely) to cause enough genetic drift that the population could no longer breed with other humans.

    It is never impossible for segregated populations to diverge, but the odds are long and thus lots of time is required to reduce the odds, and even then, there is still no certainty of divergence. So, the basic answer to the why is : it simply didn't. Why didn't I win that billion dollar lottery? Heck, even that thing which has pretty decent odds of someone winning (given how many people buy a chance), went many tries before someone actually did win.

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  • 1 year ago

    "dispite being closed off and separated from others of the same species?"

    Because that part hasn't happened. At all.

    Humans move all over and **** everywhere they go.

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  • 1 year ago

    ..

    1. The "separation" wasn't long enough for real speciation events to occur. We're talking only 60,000-70,000 years here, and our species has a long generation time compared with some other animals.

    2. Gene flow. There has been a lot of migration back and forth, visiting, conquering, and the like. Moving feet, canoes, boats, all have served to keep "human genes" in populations.

    3. Taxonomists. LOL. Classification is made according to specialists, and they do so unevenly.

    If orangutans were classified using the same rules that are applied to humans, then Tapanuli orangutans would be a "race" of Sumatran orangutan.

    If humans were classified using the same rules that were applied to orangutans, then there would be two species of humans. LOL.

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  • 1 year ago

    We humans were not "closed off and separated" for any any length of time enough to result in separate evolution. Modern humans appeared about 200,000 years ago, and we have been happily mixing genes ever since. On time scales of a few thousands of years, no human (h. sap.) group has been genetically isolated.

    The closest humans have come to isolation is Australia, which was isolated for about 5000 years (or perhaps only 3000 years). And the America separation from Asia and Europe, for about 16,000 years (or perhaps 11,000 years). The Norse settlement attempt in Newfoundland, about year 1000, isn't genetically significant.

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  • DEBS
    Lv 7
    1 year ago

    Your assumption seems to be that humans evolved AFTER migrating to all corners of the globe. Evolutionary theory takes place over millions of years. Could they not have evolved and then migrated?

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    • DEBS
      Lv 7
      1 year agoReport

      But you're assuming humans needed to evolve once separated or that there has even been time for this type of evolution to occur. Humans are able to adapt to their environment and may not have had the need to evolve like animals with lesser brains.

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  • 1 year ago

    Modern humans have been on this evolutionary branch for about 200,000 to 500,000 years. Roughly 1000 to 3000 generations. That is no where near enough to make diverging populations not reproductively compatible.

    Compare to horses and donkeys (asses). They diverged about 4 million years ago. Now they can create offspring (mules) but the offspring is reproductively limited and can’t bring the species back together.

    • Taylor1 year agoReport

      I understand that, but at least why do we physically look the same?

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