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Laying the bones bare
Finding out how flight evolved or how animals colonised the land is all about
a collision of palaeontology and genetics, discovers GrahamI.awton
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IN 1871. a now-obscure biologist
called St George Jaclcson Mivart
published On the Genesis of
Species.Asitstitlesugests, the
bookwuariposteto Darwhi's
theoryofnatunl selection,
publishedin1859.Mivarthad been
an avid Darwinian, but the more
he thought about it the stronger
his doubts grew. ID partic:ular, he
couldn't see how natural selection
could account forthe appeuanc:e
of novel structwes.
This was the start of a debate
that has raged ever since: just
what caused the majorb'ansitions
in thehlstory oflifel How, for
enmple, did birds evolve flight?
Or an1mala evolve to live on Janell
The problem is that a small,
inc:rementa1 steptowuds
mw:tures suchaswinp,feathers
or 1U11gs would appear to be
oflittleadaptivevalue,and so
wouldn't have been selected for
by evolution. Ditto the sweeping
anatomical and physiological
changes requhed to take to the
air or colonise the land As the late
palaeontologist and sdenrewrlter
StephenJayGould putit, wbatuse
is 2 per cent of a wing?
Prettymucll every major
transition hits this problem, and
creationists exploit it in their
attempts to discredit the theory.
Nell Shubin at the University
JDIRewlldeDlllllllMmdllmO
of Chicago is well placed to answer
the question.As a palaeontologist,
he pn!dicted the location of, and
then found, the fossilised remains
ofTiktaali1t roseae, a3'7s-million-
year-old transitionalfo1m.
nktaalik is what we used to all a
missing link: it is an intermediate
stage between aquatic and"As palaeontologist
andsdencewrlte:r
stephenJayGauld.
put it, what use Is
2 percent of a wing?"terrestrial animals, and one of the
best pieces of physical evidence
for the theory of evolution.
The storyofrataalik'shard·
won cllacoveryin the Canadian
AmicwasthecentRpiec:eof
Sbubin's excellmtprevious book,
Your Inner Fish. His latest book,
Some Assemb{y Requi~ plays to
his other specialism, molecular
biology, where he works to
understandhow genetics anddevelopmental biologyezplain
sw:hmajortransf.tkms-ibr
instance, how a class of regulatory
genes calleclHox ordlestratethe
development of all body plans.
His new book is a skilful and
fascinating account of how his two
very different worlds produce a
coherent answer to the z-per-cent-
of-a·wing question. Spoiler alert:
evolution rarely comes up with
anything truly new but simply
repurposes what is available.
Thus lungs evolvecl from swim
bladders, feathels from dinosaurs'
insulating fuzz, and so on. When
true novelty arises, it often comes
from an unlikely source: viruses.
Shubin covers both the
groundbrealcing sden.ce and the
sdentists who broke it, telling
a vividandhumanstoryofthe
excitement, frustration and often
sheer serendipity of progress.
1ildaalik (and Shubin) also have
acameoappearanceinanother
fine book by prolific author and
pa]aeontologist Donald Prothero
atCalifomja Polytec:hnlc StateMoleailsblalatwls
nMllallng ..... secrels
of ancient Ute Iller. rexUniversity. Shubin and Prothero
were university classmates and
remain friends.
The buddies have produced very
different books.Fanta.stic.Fossi&
is an insider's guide to finding.
collecting, identifying and
understanding fossils, including
acomprehensiw:walktbmugb
the different lifeforms that fossil
bunters might hope to unearth,
from sponges to vertebrates.
There is a lot of ground to cover,
but enough "wow" moments
tokeepyougoing,mu.chUba
real-life fosall·hunting apedition.
Did you know. for example, that
the earliest turtles had shells
on their bellies rather than their
backs? Orthatthe 15-million-yeu"
old leaves in the fossil beds of
Idaho are so exquisitely preserved
they are still green? There is all
thisandmuchmoretoenjoyin
bothoftheseboob. Ii
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