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What Darwin
didn’t know…
He fundamentally changed the way we look at life on Earth, but
Charles Darwin didn’t know everything about how evolution works.
Here, today’s experts bring the great man up to date...
Where do new traits come from? How are
Variety isn’t just the spice of life, it’s the Radiation will cause mutations too, but
main ingredient for natural selection. these tend to be short-term as they are
characteristics
Without the appearance of new traits in so damaging to a cell that they are
the gene pool, there would be nothing for removed quickly.
inherited?
natural selection to select, and evolution For the mutations that remain, natural
would grind to a halt. But it wasn’t until the selection isn’t the whole story. “The Natural selection is the process that
20th century that anyone realised that new frequency of mutations that come into a singles out the most favourable traits,
traits come from mutation. population can rise and fall simply because which are then passed on from parents
So what causes mutations? “First, of luck,” says Laurence Hurst, professor to their offspring. Known as heredity,
radiation and chemicals were thought of evolutionary genetics at the University it is the mechanism by which you, I
to be the most important causes,” says of Bath. “This is what we see with genetic or any other living thing inherits the
Christopher Wills, professor of biology at drift.” Genetic drift describes how genes characteristics of our parents. And
the University of California, San Diego. can be passed on to the next generation Darwin knew very little about how it
“It is now clear that most mutations by chance. These genes aren’t necessarily worked. So how does the process
occur through mistakes in the process of the best, but they can nevertheless actually take place?
DNA replication.” establish themselves in a population. “He suggested that different parts
of the body produced ‘gemmules’
that carried characteristics on to the
next generation,” says Professor
Wills. “[Darwin thought] the number of
gemmules produced, and their quality,
infl uenced the next generation.”
It’s a nice idea, but it’s wrong. And
it’s wrong because Darwin had no
understanding of genetics (it’s hardly
his fault – nobody had a decent grasp
of the subject until after 1900). We now
know that characteristics are passed
on in ‘particles’ of genetic information.
5 These particles are called genes, and
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the information they contain is stored
in DNA. Genes are essentially the
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instructions for what makes everyone
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who they are.
“Different forms of genes can
persist in populations for thousands of
SCIENCE PHO
generations, providing a great pool of
Changes at the genetic level, through mutations, can be passed on to the next generation
genetic variation,” Wills says.
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CIRCA 350BC 1667 1735 1766
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Aristotle arranges living things on John Ray classifi es Similar species are The Comte de Buffon describes the degeneration of

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the great chain of being, a scale organisms by grouped together to animals. The transmutation of species – evolution
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of perfection from plants to Man. physical differences. create a hierarchy – is due to the infl uence of the environment. Related
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All life was created and is He calls the similar after Carl Linnaeus species originate from a common ancestor, evolving
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‘immutable’ unable to change. types species. pioneers taxonomy. after they migrate to a new environment.
42 February 2009 www.bbcfocusmagazine.com
Focus 199 darwin2_9RB.indd 42 22/12/08 16:36:04
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