S
R
I
N
A W
E R

Y A
0
0
F

D
2 O
It’s supposed to be an unstoppable force of nature. But with most humans
living long enough to pass on their genes, has our species’s evolution come
to a halt? Here, two leading evolutionary biologists argue the case
Is Evolution
Yes
Steve Jones Now, around 99 per cent of British babies, once no wives, and no children at all. What did that
Professor of genetics they have survived the diffi cult fi rst few months, mean for natural selection?
University College London survive until they are grown up – so that the It meant there were great differences – great
differences that once fed Darwin’s mechanism variation – in reproductive success. And any
What is the future going to be like? If you believe have largely gone away. We do not need to know variation in the ability to attract a mate is raw
science fi ction it is going to be a lot like today – the details – how many perish from cholera, material for selection. Now, that pattern has
tribes, empires, wars, with a little love interest say – for the story to be clear. changed: variation in reproduction has all-but
on the way. However familiar their behaviour, Natural selection, like the driving test, is an disappeared. Most people have between zero and
though, the imagined heroes and villains of examination with two papers. The fi rst, the theory, four offspring, with the Lotharios almost extinct.
years to come tend to look quite different from is easy enough, but the practical is a lot harder. If natural selection favours variation in the
us, with giant green skulls, massive brow ridges Staying alive today is straightforward, but fi nding a ability to stay alive and to have sex, then once that
and tentacles. willing mate is more diffi cult. The range of success variation has gone it loses its power. Put the fi gures
Natural selection – the process that would is wider, too, particularly for males. Each time a for survival and for reproduction together, and
drive such a transformation – ultimately results man has sex he makes enough sperm to fertilise you get a statistic for the opportunity for natural
from inherited differences in the ability to every woman in Europe – in principle, he could selection. In the developed world, in the past few
reproduce. Once, it raged through most nations. have thousands of children. centuries, it has declined by around nine-tenths.
In Shakespeare’s day two out of every three Some still do remarkably well: Mohamed bin The result: for the time being at least (and
babies died before they were 21, and even in Laden, father of Osama, had 22 wives, and 53 keep your fi ngers crossed), there is no selection
Darwin’s time almost half did. children (and in the year of Osama’s birth he had and evolution on the Darwin model is over.
Y
Many of those deaths came from disease, six). His best known son had, at the last count, fi ve In other words, if you are worried about what
starvation or violence – and there are inherited wives and 22 sons and daughters. Utopia will be like, calm down; you are
IBRAR
components in the ability to withstand all of And in the old days, sexual inequality could be living in it now.
T
O L
them, whether it’s the blood type that gives even worse. Moulay Ismael of Morocco admitted
resistance to smallpox, or the light skin that to 888 children. There was, needless to say,
Steve Jones’s latest book
allows some people to synthesise vitamins more than one Mrs Moulay. As a result, around a
Darwin’s Island is out this month,
published by Little Brown
SCIENCE PHO missing from the diet. hundred of his male fellow citizens must have had
1865 1893 1910-1915
Gregor Mendel shows that characteristics August Weismann proposes that Thomas Hunt Morgan’s lab
are inherited as discrete particles: each acquired characteristics (any attribute uses classical genetics to
one of an offspring’s characteristics is not that isn’t in your genes) cannot be trace the history of mutations.
a ‘blend’ from its parents. It is not until inherited. So even if you chop a mouse’s They also discover that genes
1900 that the particles are called genes. tail off, its offspring will still have tails. are located on chromosomes.
44 February 2009 www.bbcfocusmagazine.com
Focus 199 darwin2_9RB.indd 44 22/12/08 16:36:17
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12