The last human species: rethinking why the others disappeared
By Victoria Travers
Modern humans, Homo sapiens, are the sole surviving members of the genus Homo. However, around 300,000 years ago there were at least nine other human species that were present across Africa, Europe and Asia. For most of our evolutionary history, we were not alone. So, why are we the only ones that survived?
For decades, the popular answer, and the one that many people still instinctively think, was relatively simple: we were smarter. We were supposedly better at innovating and adapting, framed as if we were the ‘superior’ humans. However, modern palaeoanthropology pushes strongly against these ideas. Not only are they often unfounded, but they were also shaped by colonial ideologies.
For much of the twentieth century, Neanderthals were portrayed as brutish and intellectually inferior, a caricature rooted as much in ideology as in science. Early evolutionary models often framed human evolution as a ladder, with ‘primitive’ apes at the bottom and modern Europeans at the top. Today, that framework is deeply outdated.
For most of our history, we shared this planet with other kinds of humans
One explanation that has attracted a lot of scientific attention focuses on diet. Some researchers have argued that Homo sapiens possessed greater dietary plasticity, the ability to exploit a wider range of foods, giving us a survival advantage. Yet, isotopic analyses of fossil bone collagen revealed the types of food ancient humans consumed, complicating this claim. Stable carbon and nitrogen studies show significant overlap between Neanderthals and early modern humans. Both species occupied high trophic levels in many regions, consuming large quantities of meat. Evidence from dental calculus even shows that Neanderthals processed plants, cooked starches, and possibly consumed medicinal herbs. In coastal environments, both groups exploited marine resources. Rather than one species being rigid and the other flexible, the evidence increasingly suggests that multiple human species were adaptable and opportunistic.
Archaeology further undermines the stereotype that Homo sapiens were always the most successful Homo species. Neanderthals produced sophisticated Mousterian tools, controlled fire, and manufactured birch tar adhesives, a complex, multi-step chemical process requiring precise temperature control. They created personal ornaments and, in Spain, cave art that may predate the arrival of Homo sapiens in Europe. There is evidence for deliberate burial and possible symbolic behaviour. These are not the hallmarks of a cognitively inferior species.
Genetics further blurs the boundaries between species. Genomic studies show that most non-African modern humans carry around 1–2% Neanderthal DNA, and some populations in Melanesia carry up to 5% Denisovan DNA. These were not rare accidents; interbreeding occurred multiple times over thousands of years, and some of the inherited genes influence immune responses and even altitude adaptation in Tibetan populations today. If we apply the most widely used species model for living organisms, the biological species concept, which defines species as populations whose members actually or potentially interbreed in nature and produce fertile offspring, the argument for strict separation becomes shaky. Morphological differences certainly exist, Neanderthals were more robust, with distinctive cranial features, yet variation within modern human populations is also substantial. This is why some scientists now debate whether Neanderthals and Denisovans were truly distinct species or regional populations within a broader human lineage. The question therefore shifts from whether we simply outcompeted other humans to how far they were already, genetically, part of us.
If other human species were intelligent, adaptable and capable of interbreeding with us, then their disappearance may not reflect inferiority at all. Climate instability during the Late Pleistocene created rapidly shifting environments, and small population sizes made groups vulnerable to demographic collapse. Most researchers now think there is no single cause, but a combination of environmental instability, small population sizes and repeated contact with other humans. Competition, disease exchange, and gradual genetic assimilation likely all played roles.
The image of human evolution as a straight line, primitive to advanced, ape to man, has long been replaced by something far messier. It is important when discussing this topic, not to view the surviving species as the pinnacle, but simply the last surviving branch. Under different conditions, it could have just as easily been another Homo species that persisted while we disappeared. The story of human evolution is not one of inevitable superiority. It is one of coexistence, interaction, and complexity. For most of our history, we shared this planet with other kinds of humans. And in a very real sense, we still do; genetically, they remain part of us.
Image: Haeckel, Ernst Heinrich Philipp via Wikimedia Commons
