Most readers of newspapers or magazines are likely to have
encountered evolutionary explanations and worse, justifications for almost any
human activity, from rape to raw meat diets. There are several things wrong
with these melodramatic logical leaps. In
Paleofantasy, Marlene Zuk masterfully, and with
characteristic bluntness, debunks every fallacy and fantasy, walks you through
the basics of evolutionary theory and makes you laugh out loud, all at the same
time.
The subject matter for this book is brilliant, because as
humans, which one of us isn’t really quite fascinated by our own history, and
what it might mean for our present and future behaviour? There are a slew of
well-written introductions to evolution on the market, many of which spend a
great deal of effort trying to convince readers that evolution does indeed
occur. There is nothing wrong with these books, but they tend to attract
readers who are already members of the evolutionary choir, rather than people
who might otherwise consider themselves largely uninterested in science. Almost
anyone would be interested in questions like: Are humans still evolving? What
does evolution tell us about what we like to eat, do for fun or why we get old
and die when we do? In answering these questions, Zuk brilliantly explains both
the key theory and some fairly abstruse methodology with such clarity and
humour that without realising it, the reader is given a first class grounding
in modern evolutionary biology. That is what makes this book the perfect gift
and ideal reading in an introductory course for non-biology majors while still
being great fun for any biologist, who must often trot out similar vignettes for
friends and family.
One of the most commonly encountered confusions are
arguments along the lines of “our ancestors evolved to do X (where X can be
running barefoot, or being promiscuous) therefore we are justified in doing X.
Paleofantasy steps through aspects of human life, from diet, to exercise, sex,
birth, death and disease, and two threads run through the book: firstly, that
what is “natural” or “evolved” does not equal what is good, and secondly, that
it’s usually jolly tricky to know what is “natural” in our evolutionary past.
Advocates of paleolifestyles seldom agree on what is
natural, and for good reason. There simply isn’t much evidence for a single,
static and decipherable Flintston-esque evolutionary past for humans, so it’s
anyone’s guess what our ancestors did, which allows for personal preferences to
run amok. Zuk is particularly good and finding stunningly funny quotes from
earnest Paleo-bloggers who rhapsodize over the beneficial effects of subsisting
on pork belly or doing spontaneous busts of press-ups and sprints to simulate
the heaving of boulders and the need to flee from enraged rhinos in our
so-called evolutionary past.
Zuk’s main point, which she dedicates a chapter to, is that
evolution can happen a lot faster than you might think, and that it can occur
at very different speeds. So even if there were a relatively long period of
environmental stability in our past, that doesn’t mean we haven’t changed
genetically since the invention of agriculture. Besides, humans pride
themselves on their flexibility and ingenuity, so it should come as no surprise
that in our evolutionary past, we were probably rather good at moving about,
living in a wide range of places and with a wide range of social systems. We
are generalists like rats, and we like to think we’re smarter. This chapter on
rapid evolution is probably my favourite, because it introduces some of the
most classic examples of rapid evolution like finch beaks and viruses, but also
displays some of Zuk’s own work on Hawaiian cricket males who have evolved in
the space of a few years to stop serenading females because the song also
attracts deadly parasites that would otherwise kill the males before they had a
chance to mate.
In the very next chapter, Zuk discusses the poster child of
human evolution – the ability of cattle-herding populations to digest milk as
adults. Not only is this example a jolly good bit of evidence for rapid,
culturally imposed (you could say self-inflicted) human evolution, it also
gives Zuk the chance to explain some tricky methodology with admirable clarity
and simplicity. And it will give readers a good idea of just how biologists
work, from collecting the blood and spit of people around the world to the logic
underlying computer tests.
Peppered throughout the book are not just pictures of how
science is done, but also an affectionate but perceptive portrayal of
scientists as people. Starting with her own delightfully distinctive,
no-nonsense style, wry humour and sensible brand of feminism, Zuk is superb and
showing how every scientist has his or her own (often enchanting) biases and
mannerisms. She lets slip that Linnaeus, father of modern biological
classification, decided to name the main plant groups according to the numbers
of husbands or wives each plant had. Similarly, the Grants, who measured
natural selection in action on Darwin’s finches in the Galapagos come alive in
her anecdote about their group meeting on returning from the field after a
massive El Nino changed the landscape dramatically from brown and barren to a
verdant paradise. The Grants and their students could barely contain themselves
at the sight of photos, excitedly remarking upon every tree, resplendent in
unaccustomed greenery. In contrast, Zuk, then a student from a different lab,
found this so tedious she had to slip out. That anecdote and many others,
captures both the thrilling and the mundane in science, practised by subjective
scientists. For a superb book on the Grants' work, I highly recommend
The Beak of the Finch.
Paleofantasy doesn’t simply showcase instances of evolution
by natural selection as demonstrated by Darwin’s finches. Zuk deals directly
with the fact that evolution is simply defined as change, and so can occur in
different ways, of which selection, whether natural or human is merely one. For
those who might want reassurance that this is indeed a good introduction of
evolutionary theory, Zuk explains concepts like drift, the role of contingency
and history in evolution, adaptive landscapes, arms races and the ideas that
evolution is a tinkerer. If these phrases are Greek to you, read the book. She
also puts to rest the notion that evolution is in anyway directed, or that any
living thing today could be “more evolved” or superior to any other living
thing, since they have all been evolving for equally long.
The only aspect of evolution I would have liked to see more
of in this marvellous book is conflict. Perhaps this is because Zuk didn’t wish
to put off people with a rosier view of human nature, but as we’ve established,
nothing in evolution prescribes or justifies our moral choices. She does
present the intriguing notion that humans have an unusually extended childhood
as a way for parents to have a lot of relatively cheap labour. However her
chapter on family remains relatively silent on the converse scenario in parent-offspring
conflict, where children can be thought of as little machines for manipulating
parents into caring more for them than for their current or potential siblings.
There is a delightful extension of the theory behind
parent-offspring conflict, proposed by David Haig, which essentially explains
much of behaviour or even foetal growth in terms of conflict between genes
inherited from mums and dads within an individual’s body. It’s as if your
parents could extend their evolutionary battle to your body, rather than just
tussling over who is left holding the baby. For instance,
Haig just proposed
that genes inherited from fathers are the copies that make babies cry more at
night, the better to exhaust mum so she takes longer to produce a competition
in the form of a sibling. In contrast, copies of the same genes inherited from
mum would make babies less likely to cry. This, and all other instances of
Haig’s conflict explanation for “genomic imprinting” – the phenomenon where a
gene’s actions differ depending on the sex of the parent they came from, rather
than the actual gene sequence – is contingent on males being unable to
guarantee that they will always be the exclusive mate of a female. As a result,
genes from fathers will benefit if they can cause offspring to behave in
relatively selfish ways, such as growing rapidly in utero, while genes
inherited from mothers can best counter this by having the opposite effect on
offspring, such as silencing signals to grow. It’s not that mothers don’t need
healthy offspring, but they would pass on the most genes if they could divide
up their lifetime’s resources evenly across an optimal number of children. In
contrast, males who might only father one or some of that mother’s children, will
have not genetic interests in her other progeny, and their genes would do best
if they could cause their offspring to exploit mum as much as possible, to the
detriment of mum’s other offspring. My favourite popular books on the general
subject of conflict (and cooperation) are still
The Selfish Gene and
TheExtended Phenotype by Richard Dawkins. Please don’t get put-off by his
later polemical pieces like
The God
Delusion.
Zuk herself is arguably most famous for the “Hamilton-Zuk
hypothesis”, which is founded on the continual conflict between sexually
producing organisms and their parasites. The notion is that the main way for
relatively slowly reproducing things like humans to stay one step ahead of
bacteria and viruses is to keep coming up with new combinations of immune
defences encoded in our genes. These genes can be reshuffled, where genes from
our mum and dad are literally recombined every time one of us makes eggs or
sperm, and then they get paired with a new mixture when we have sex. The
sexiest mates should be the ones that will help make children with the most
varied combinations of genes, the better to confound those rapidly reproducing
parasites. If you want a more thorough treatment, you should read Zuk’s book
Sexual Selections. But if you just want
a good general Christmas present for anyone who likes reading, please consider
Paleofantasy.
