Darwin’s ‘On the Origin of Species’

Are humans different?

Are we different from the rest of the natural world?

Can biological mechanisms explain all aspects of human biology, or do we need to call upon special processes?

We are used to thinking of human beings as the pinnacle of life. Christianity, Islam and Judaism all say that God created us in his own image. When Darwin published ‘On the Origin of Species’, he made no specific mention of human evolution; the idea that we evolved from apes was radical in the extreme.

And the idea that the extraordinary abilities of humans – language, intelligence, emotions, empathy, love – can be put down to random changes in DNA can seem difficult to accept.

Genes

But is there any reason to believe that these traits are ‘special’ one-offs that we alone have? The obvious thing to do is compare ourselves with other animals – such as chimpanzees, our closest living relatives.

We shared a common ancestor with chimpanzees around seven million years ago. Since then, we have diverged markedly (although half of our genes still code for identical proteins). We have less hair and bigger brains, and we’re more intelligent.

By comparing genome sequences, researchers can identify genetic differences between the two species and particularly regions of the genome that are diverging rapidly between humans and chimpanzees. It is noticeable that these often include genes influencing brain development.

A further rapidly evolving region of the human genome, HACNS1, controls limb development. It may have had a role in the evolution of humans’ opposable thumb. 

In addition, studies of human genetic variation around the world, such as the 1000 Genomes Project, have identified differences that can act as a source of variation for natural selection to act upon and may account for some of the differences between present-day human populations. 

Brain power

So much for genes. What about our mental and other skills? Here, again, there is little that seems uniquely human. Other animals show simple ways of communicating with one another, mice have recently been shown to experience a type of empathy, crows have been seen to use tools, and rats have been shown to understand the motivations of others.

The most contentious area is consciousness. Is this what distinguishes us from other animals? Perhaps. But consciousness is difficult to define and study (see our ‘Thinking’ issue), and the difference may be one of degree rather than presence/absence. You can debate this idea with our ‘Big Picture Debates the Brain’ app.

Scientifically speaking, then, purely biologically forces seem perfectly able to explain the creation of human beings.

Lead image:

Darwin’s ‘On the Origin of Species’.

MaropengSA/Flickr CC BY

References

Questions for discussion

  • Do you think humans are ‘different’? In what way? Are they different in ways that can’t be explained biologically?

About this resource

This resource was first published in ‘Evolution’ in January 2007 and reviewed and updated in December 2014.

Topics:
Genetics and genomics, Neuroscience, Psychology
Issue:
Evolution
Education levels:
16–19, Continuing professional development