IT IS finally time to kiss goodbye to the idea that humans are qualitatively different from other animals. The notion has been ingrained for centuries, yet in recent years research has found overwhelming evidence to the contrary. We are not as unique as we thought.
Hardly any aspect of our biology is distinctly human. There is no definitively human type of neuron, and while it is possible that there are a few human-specific genes, they alone cannot explain the differences between 鈥渢hem鈥� and 鈥渦s鈥�. Recently, we have found that even most human mental tricks have some rudimentary analogue in the animal world and most elements of human culture have a resonance in other species.
To anyone schooled in Darwinism, this should come as no surprise. Humans sit on a tiny twig of the much larger tree of life. Evolutionary theory tells us that our brains are not wholly different from the brains of other animals, so what they do should not be wholly different either. In fact, it would be a problem if it were.
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Still it is a shock that so many differences between humans and other animals are of degree, not kind (see 鈥淲hat鈥檚 so special about humans?鈥�). The fact that it has taken us so long to erase the thick line between ourselves and the rest of the biosphere tells us much more about how we like to think of ourselves than it does about the science or the research findings.
So how should we now think of ourselves in the light of all the evidence? It is not enough to say that humans, with all our differences, are at one end of a simple continuum. A linear relationship would not solve the puzzle of human material culture and symbols, which are so much more astonishing, pervasive and dominating than those of any other species. We may no longer be qualitatively different, yet what other species has flown to the moon, invented theatre, or makes birthday cake?
Clearly, just because the differences are not qualitative does not mean they do not matter. Yet how do we discover how much each one matters? One valuable idea is that it is not just what you have as a species that matters, but how you put it all together. Why, for example, can鈥檛 orang-utans, chimpanzees and bonobos speak like us? They are missing at least two things: human grammatical ability and the athletic ability of our vocal tract. What they do possess is the ability to create meaning, as evidenced by their gestures. Put these three things together and you get something that starts to look like human language.
Though other animals possess many of the parts of the language whole, they do not have human language. The same is probably true for all aspects of cognition. Until we can better gauge the impact of all those degrees of difference, breaking down our abilities into component parts and seeing which creatures share them with us seems to be the best way to discover what sets humans apart.
Human Evolution 鈥� Follow the incredible story in our comprehensive special report.