Humans, all alone

Recently, a near-perfectly preserved fossil of a skull was identified as that of a newly discovered human-like species Homo longi or "Dragon Man"

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” This famous quote is often misattributed to “father of evolution” Charles Darwin and his 1859 book On the Origin of Species but its essence is true, nonetheless.

Recently, a near-perfectly preserved fossil of a skull — that sits in the Geoscience Museum in Hebei GEO University — was identified as that of a newly discovered human-like species Homo longi or “Dragon Man”.

The findings, published in The Innovation, suggested the Homo longi lineage — and not Homo neanderthalensis (Neanderthals) — may be the closest relative of our species, Homo sapiens, thus potentially reshaping our understanding of human evolution. Though the jury is out on which of the two extinct species is our nearest cousin, it begs the question why only our line survived.

“We have one human species right now, and historically, that’s really weird... Not that far back, we weren’t that special but now we’re the only ones left,” Nick Longrich, an evolutionary biologist at the University of Bath, was quoted as saying in an article on Live Science. Only around 15,000 years ago, our ancestors shared caves with another human-like species, the Denisovans and around 300,000 years ago, there were estimated 8-9 species remarkably close to us, humans. The “Dragon Man” cranium is believed to be 146,000 years old. We weren’t alone until we were alone but why?

We can’t give credit to our smartness alone. Yes, our brains are relatively big and massively contributed to our rise but other human-like species were no slouches either. Modern humans and Neanderthals show an average cranial capacity of around 1400–1500 cc and probably a bit larger for the latter group. Homo longi, too, had a massive brain at roughly 1,420 cc.

Like early humans, our close relatives, too, fashioned tools and weapons, and strategised to hunt animals; they tended their injured and tried to fix broken bones; they buried their dead. Our ability to create or communicate weren’t ours alone. Our ancestral relatives were anything but stupid, and yet only we flourished.

In Nature Human Behaviour, Patrick Roberts and Brian Stewart, based on comparison with other members of the genus Homo, argued “our species developed a new ecological niche, that of the ‘generalist specialist’”. They stressed Homo sapiens have “unique ecological plasticity” (in simpler terms, we are very good at living in different parts of the world, from mountains to plains and Siberia to Sahara).

According to Roberts and Stewart, fossil records show our ancestors expanded to more difficult niches than their hominin predecessors and contemporaries by 80,000 to 50,000 years ago. But could this be the only reason? Probably not.

Ancient humans were culturally complex and behaviourally flexible and that likely helped them adapt to a wide range of environments. Anthropologist Melanie Chang argued demographic changes (increasing population) drove Homo sapiens’ innovations, helping them occupy unconquered regions (Inverse).

Early humans lived in socially close gatherings and frequently exchanged their experiences, knowledge, and technology with outsiders, while their palaeolithic cousins lived in isolated groups (like modern great apes) and weren’t as socially strongly knit as us. And this might have tilted the scales massively in favour of Homo sapiens when it came to clash for territory and food, and reproduction.

The answer to their extinction could also lie in our population growth. Once humans became cooperative hunters, we had no predators; without predation controlling our numbers and any family planning, our population grew fast to exploit the resources, forcing others to the edge.

According to estimates, the population of Neanderthals never exceeded 100,000 and living in small isolated pockets meant more inbreeding and a small genetic pool (there was rampant inbreeding among Homo sapiens, too). Probably they and others like them were already endangered when our ancestors first met them after leaving Africa, and also, we might have dealt them a fatal blow by passing on a simple flu virus during interactions.

And yes, our species interacted with other hominins and also interbred. The current generation carries genes from our ancestors’ encounters with Neanderthals, Homo floresiensis (Hobbits), and others; similarly, the other groups (especially Neanderthals) carried some modern human genes from even earlier encounters with vanished groups. 

In 2010, scientists led by Ed Green of the University of California, after comparing ancient and modern sequences and tallying up shared sites and mutations, revealed the Neanderthal DNA makes up 1-4 per cent of the genome of people today of non-African descent — evidence of interbreeding in Eurasia beginning 60,000 years ago. They also discovered the Denisovan DNA makes up 3 per cent of the genome of people in Papua New Guinea and Australia. They all lived in us!

Today, we search star systems to find intelligent species, like us. Just remember our ancestors had found many until they were all gone. And also ponder: We are the only survivor of a diverse family tree; are we the last twig or final blossom?