scienceillustrated.com.au | 25specific day when Species 1 ends and
Species 2 takes over. No hairy Homo
erectus suddenly gave birth to a weirdly
bald and intelligent Homo sapiens. It
happens over time. Extremely long
periods of time.
Critics of evolution like to use the
example of the chicken and the egg
though, because that extra step – birds
are “born” on one day, then “hatch” on
a different day – adds extra confusion. If
a proto-chicken lays an egg that hatches
into a chicken... was that a proto-chicken
egg, or was it a chicken egg?
If they’re being particularly belligerent,
these critics will point out that the internal
machinery required to build an egg is very
complex, so how could a thing-that-wasn’t-
a-chicken possibly include the right
machinery inside it to make a chicken egg?
And this is where the evolutionists step
in and try – again – to explain that the bird
we call a “chicken” didn’t just suddenly
pop out of a dinosaur egg or something. It
has a bird ancestor which already laid
eggs. And before that, eggs were used by
dinosaurs of course, and even earlier, by
amphibians too.
So obviously, “the egg” as a tool for
helping baby chickens develop to a size
large enough so they can survive when they
finally hatch, came first.
But ah, say the critics. We’re not asking
if the chicken’s ancestors laid eggs. We’re
asking how an animal that needs to develop
in an egg could ever come out of an animal
that wasn’t the same species.
One day, a bird we now recognise as a
chicken, had to be born. There had to be a
“first chicken”. But if chickens can only
hatch out of chicken eggs, how did this
happen? How could a, let’s call it a
neanderchicken, lay a chicken egg?
To answer this, it’s helpful to realise
there’s no such thing as a chicken.
Oh fine, semantically of course there are
chickens. My mother has some. But in a
biological sense, this idea of organising
animals into discrete species and saying
“that animal there is a grizzly bear, and that
one there is a red kangaroo” is very
human, and nature doesn’t really pay
that much attention to it.
What each of us are, in an
evolutionary sense, is the organism
that has been constructed by a set of
genes. Our genes provide the
fundamental instructions for what we
look like (though our environment
affects the fine details, of course).
If you look only at genes over time,
it’s not exactly straightforward to tell
where one species gives way to
another. A million generations of a
horse-like creature might show a slow
loss of one particular set of genes,
while a mutation elsewhere slowlybecomes dominant and gives the horse-
like creature, say, hooves.
There’s no point in time where a
horse with no hooves popped out a foal
and said “Look at this freak’s feet!” If
you had a time machine and made
multiple stops, say every few hundred
thousand years, you’d need to
photograph thousands of horse-feet and
then arrange them chronologically.
Only then would you see a very slow
and gradual change from soft toes to a
single, hardened hoof.If chickens must hatch
out of chicken eggs, how
could there ever be
a fi rst chicken?The large image is a chicken,
and the smaller (right, inset) a
grey junglefowl. The family
resemblance is very clear.