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It’s lonely at the top – the last human species

25 September 2011

Homo neanderthalensis

"I know, doesn't it look cool? I'm thinking of calling it 'blonde' - it's going to be BIG!"

I think one reason for the notion that we are so special comes from the fact that there’s only one species of humans on the planet. There is such a wide gap in intelligence, culture and technology between us humans and other intelligent animals, that we could be forgiven for believing that we are absolutely unique.

This has not always been the case, however. Just 50,000 years ago almost half a dozen species of humans (including us modern Homo sapiens) inhabited Earth. Back then, you could come across fast-running Homo erectus and hobbit-sized Homo floresiensis in Asia, Denisovans in eastern Russia and Neanderthals in Europe. Our planet was crawling with species of humans, each with their own cultures, technology and languages.

Homo erectus

"No, I'm Homo ERECTUS. Try to keep up, will you?"

As we moved out of Africa and into the Middle East, the first ones we would have encountered would have been the Neanderthals. They were short and stocky, with pale skin, blonde or red hair (and probably freckles) – a stark contrast to our long, slender African bodies with dark skin and hair. The Neanderthals had been a highly successful species with many adaptations to the Glacial European landscape, but as our own kind expanded westward they disappeared.

Further east, in modern-day Siberia and Mongolia, we would have come across the Denisovans. Nobody knows what they were like, as all we’ve found is a finger bone and a tooth, but DNA suggest they were a sister species to the Neanderthals. It is therefore highly likely they also were pale skinned and fair-haired.

Homo floresiensis

"Who is this 'Frodo' that you speak of?"

Down south, in tropical Asia, we might have encountered a real oldie: Homo erectus, the most long-lived human species of all and an offshoot of our own ancestor Homo ergaster.  Whilst ergaster never left Africa, erectus did, and populated most of the Asian continent for several million years. They were tall and slender like us, used fire and tools, and lived in closely knit family groups as hunter-gatherers. They would have been awesome runners, easily as fast as a modern-day Olympic athlete.

Far east in Indonesia we might have found the hobbits: Homo floresiensis. At just 1m (3 ft 6 in) tall, they were the smallest of all humans, and probably lived as hunter-gatherers deep in the tropical rain forests.

We can only imagine what it would have been like for our ancestors to meet these ‘other’ humans. Did we see them as people? Or perhaps as trolls and goblins? Did we trade with them or did we fight them? And why are they all gone and we’re the sole survivors?

Homo sapiens

Is this boy an actual descendant of the mysterious Denisovans?

As it happens, we aren’t. Or at least not entirely. Recent studies have shown that all non-African humans have a percentage of Neanderthal-DNA in their genome. We’re literally carrying around the remnants of the Neanderthal populations in our genes. Perhaps that is where we got the genes for blonde and red hair from? And people living in Papua New Guinea can boast another set of genes: those of the Denisovans. In fact, they are the only known population that have both dark skin and fair hair.

So regardless of if we saw these other species as ‘humans’ or not, we did mate with them. And perhaps that is how they disappeared – they weren’t killed or out-competed. Instead they were simply absorbed by our growing population, and their species were assimilated. Which would make us kind of like the Borg – but a kinky and oversexed type of Borg that would do whoever they came across.

11 Comments leave one →
  1. 25 September 2011 22:24

    I’m reading this while watching X-Men First Class resulting in some bizarre introspection on the matter. I am also thinking of something I read about all blue-eyed individuals being linked to the same ancestor. If true, that guy must have been VERY popular.

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  2. 25 September 2011 22:52

    Side-Note: None of the mutations on X-Men are very practical. Now they are just bickering with each other and blowing things up. I’m going to go try to move things with my mind.

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  3. 25 September 2011 23:12

    I thought we were all so condensed because of some event like a freeze that killed off everyone else. No one ever suggested we absorbed other species like the Borg. I wonder if I have never heard this theory before because it isn’t that sexy to think that we are the human version of mules.

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    • 26 September 2011 04:26

      To be fair, it’s not known if we cross-bred with ALL other species of humans. But we’re definitely a hybrid species. Except the Africans – they are pure Homo sapiens.

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  4. 27 May 2012 20:03

    We also know that the Neanderthal parts of our genes came wholly from male Neanderthals, as the genes you mention are only transmitted via the Y chromosome. It’s possible that male homo sapiens also interbred with female Neanderthals, but no such gene combinations exist. Presumably because the female Neanderthals would have returned to their tribes, which eventually died out. Genetics is neat!

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    • 27 May 2012 20:16

      I did not know that. Although it seems odd that only genes from the X or Y chromosomes would be transferred between the two species. Perhaps we’re yet to discover the other genes? And yes, genetics is indeed neat!

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      • 27 May 2012 20:50

        As I understand it, there are many genes which are limited to either the X or Y chromosomes. For instance, colorblindness is always on the X chromosome, which is why women rarely suffer from it (since they have a backup if the one is wonky, where as men only have one X).

        Because we only have Y chromosome Neanderthal genes, it means that Neanderthal men mated with Homo sapien women and produced successful offspring. The absence of X chromosome Neanderthal genes means one of two things. Either offspring of Homo sapien men and Neanderthal women were sterile, like ligers and tigons, or no such offspring survived. I think this is probably the case– females would probably return to their tribe and family, rather than join the males. So Homo sapien women with a half-Neanderthal baby would return to the Homo sapien tribe– the race that survived. There could have been Neanderthal women with half-Homo sapien babies, but as that race died out, no such remnant exists.

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        • 28 May 2012 20:19

          Interesting. But how about the X-chromosomes from the Neanderthal males? In 50% of the cases of interbreeding, a Neanderthal male would have transferred an X-chromosome instead off a Y-chromosome. Why didn’t any of those genes survive?

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          • 30 May 2012 01:52

            That’s a great question! There are two different ways we can do genetic tracking. One is mtDNA tests, which are conducted through mitochondrial transmission. The other is Y-line tests, which use a distinctive haplotype limited to Y chromosomes.

            With the Neanderthal questions, we have Neanderthal genes present in Y chromosomes. However we do not have any in mitochondria, so we can infer that no female Neanderthal genetic material survived into the modern human genome.

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            • 30 May 2012 03:20

              I see. So somehow, for some reason, the female line disappeared. Fascinating!

              Although that means we still don’t know how common Neanderthal DNA is in modern humans, do we? From other chromosomes, I mean?

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