Don't write evolution's obituary yet...

Are we as good as it gets in terms of human evolution? Is natural selection no longer working on the human race?

Steve Jones, Professor of Genetics at University College London, kicked off a new lecture series at UCL yesterday stating that, yes, evolution is over in humans. He also gave an interview on The Today Programme and wrote a column in the Telegraph.

Many other geneticists might beg to differ.

‘Steve seems to be making two points,’ says Dr Gil McVean of the Wellcome Trust Centre for Human Genetics [WTCHG] at the University of Oxford. ‘First that a reduction in paternal age leads to a reduction in input of new mutations, and second that the modern environment has reduced the power of natural selection.’ 

‘The first point is a bit strange,’ he says. Men are making sperm all the time, so if they have children at a younger age, the sperm cells are the result of fewer cell divisions than in older fathers. ‘This may reduce the rate of mutation per generation,’ Gil agrees, ‘but it also reduces the time between generations.’

More generations would allow more mutations to occur over a certain time span.

'This is important because there are many types of mutation and only a few seem to show a strong paternal age effect,’ Gil says. Some mutations are strongly influenced by genetic recombination on the maternal side, and these will be unaffected by the age of the father. ‘If anything, the trend for an increase in maternal reproductive age will lead to an increase in these types of mutations.’

It is undeniable that modern agriculture, increased travel and trade between populations, and increased life expectancy in Western societies has led to a reduction in the power of environment-based natural selection. ‘But you have to remember that worldwide millions of children under reproductive age die each year of infectious diseases like malaria, tuberculosis, etc.,’ explains Gil.

This means that there will be a selective pressure on versions of genes that offer a better chance of survival. ‘With the spread of relatively new pathogens like HIV1, it seems to me that the vast majority of the world's population is very much at risk from the power of natural selection,’ he says.

It's not just developing countries where natural selection is still acting.

‘In Western societies, there is a strong trend to increased maternal age and, with it, increased problems of infertility,’ says Gil. Genetic influences that lead to fertility being maintained at older ages will also be subject to natural selection and there is direct proof of this in Iceland.

Dr McVean’s research focuses on the genetic variation seen in human populations, based on the large amount of data now being accumulated on human genomes. With the HapMap and 1000 Genomes Project, we are seeing that humans differ not just in individual changes in DNA sequence, but in whole insertions, deletions, and repeats of large chunks of DNA. The picture being built is one of a very dynamic, changing human genome.

So there is variation in the genetic makeup of the human population, mutations are continuing to occur, and there are still selective pressures on these genetic variants. Evolution would appear to be alive and well.

‘We may have changed the environment to get rid of old selective challenges, but we have also created more,’ states Gil McVean. 

Homo habilis, yesterday. Image via Wikimedia Commons. 

Your comments

• just a comment

  ozan | 21 Oct 09

  evolution is a process and it's continuing...

• Amizing

  Nisse Eriksson | 24 Jan 09

  Rejoice, African! Do not becry your fate, you are in the midst of the awesome...

• medicine

  Ryan | 06 Jan 09

  I agree with those point!

• Back to basics

  Gustav Clark | 07 Dec 08

  McVean picks out many of the direct evolutionary pressures on us, but there is a...

• Wood waters it down.

  David Kydd | 09 Oct 08

  It does nobody a service to muddle. Wood misrepresents Jones, who said in the...

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