The fossilised remains of coelacanths are well known in sedimentary
rocks from 400 million years old to 65 million years old, but they have
not been found in rocks younger than this. Their fossil record mysteriously
dries up, coincident with the demise of the dinosaurs. So it was generally
believed that coelacanths were extinct, having joined the end of the Cretaceous
queue to meet their maker along with dinosaurs, pterosaurs, ammonites and
many other animals.

In 1938, however, a stray coelacanth, by a stroke of luck or misfortune
– which depends on whether you’re a coelacanth or an ichthyologist – met
a wandering trawler skippered by a keen-eyed sea dog with an interest in
the unusual. The first living coelacanth had been found.

Living coelacanths are large, beautifully ugly, bluish-grey fish with
silver blotches and bizarre looking fins. They live in deep water off the
Comoros in the Indian Ocean. The first specimen almost failed to make it
into the history books. The discovery was landed at East London, South Africa
on 22 December 1938. With Christmas three days away the prize was almost
turned down by Marjorie Courtenay-Latimer, the curator of the East London
Museum who had been diligently collecting fish for her museum. The new specimen
was not recognised as a coelacanth at first, merely as an unfamiliar fish.
But it was not long before brains were being racked to determine its true
affinities. A letter, including a sketch, was sent to James B. L. Smith,
the only practising ichthyologist in South Africa at that time, but it did
not reach him until early January. It was Smith who realised that the fish
– by now rather a smelly one – was something very special indeed.

To cut a long, but gripping, story short, in a letter to the journal
Nature, Smith christened the new fish Latimeria chalumnae after both its
discoverer Courtenay-Latimer, the East London curator, and the Chalumna
River near where the fish was caught. At the age of 41 Smith had finally
made history – Latimeria made front page news.

Several years passed before another specimen was caught, this time by
a fisherman off the isolated archipelago of the Comoros, a French colony
in the Indian Ocean. In what must have been the most remarkable reason for
the invasion of another country’s sovereign territory, the South African
president authorised an airborne operation to go and steal a fish. (They
were quite nice about it, and there was no bloodshed).

Nearly 40 years later Latimeria is still making headlines. It first
appeared on television when David Attenborough’s Life on Earth series included
a short piece in which a dying specimen was filmed in shallow water off
the Comoros, and then again in the late 1980s when Hans Fricke, exploring
from a submersible craft, filmed living coelacanths in their natural habitat
about 200 metres down.

So what is it about this particular living fossil that attracts so much
attention? The answer probably lies in media hype. Latimeria has been claimed
to be a missing link between man and fish – the ancestor of the first creatures
to leave the water and breathe air – just as the fossil Archaeopteryx was
claimed to be the missing link between reptiles and birds. The term missing
link is wholly inappropriate, but both are nevertheless exceedingly interesting
animals.

What is meant by ‘living fossil’? The term is difficult to define, but
one could say that they are living organisms that do not differ significantly
from their fossil counterparts. To this group belong magnolia and ginkgo
trees, tapirs, the Australian lungfish, a variety of molluscs including
the nautilus and, of course, the coelacanth itself. But coelacanths are
special as they belong to an elite subset of organisms that were known to
scientists from fossil remains long before they were discovered alive and
well.

Calling coelacanths living fossils is perhaps a little unkind. Yes,
they do have a fossil record going back 400 million years, but they have
not been doing nothing for all that time. They did diversify, as Thomson
explains. They adapted to a range of aquatic environments, from marine to
freshwater, from the shallow to deep. Some were small, others of gigantic
proportions, and every bone in their bodies underwent some modification
of shape or size or both. It is just that, despite all of these changes,
they always looked like coelacanths, and still do. Contrast this with theropod
dinosaurs which have been around for half this length of time and now look
like starlings, ostriches and humming birds.

How significant was the 1938 discovery of the first living coelacanth?
It is difficult to say. But Thomson, in his very laid-back and readable
style, goes to considerable lengths to assess its importance to the local
human community where it was first found, to the scientist who first described
Latimeria, and to the scientific community at large.

Thomson’s book is as much about the philosophy of science as it is about
coelacanths. He examines the coelacanths from the earliest days of their
discovery, from the time they first hit the headlines bringing a mixture
of fame, scientific respectability and a not inconsiderable degree of trepidation
to its describer. (What would you do if by accident you chanced on the first
living pterosaur? Answers on a postcard, please.) Thomson reveals the politicking
behind later discoveries in the French colonial territory, and enters the
ethical argument over whether or not coelacanths should be caught at all.
This is all for good reason.

With so much public interest in Latimeria, it is no surprise that scientific
altruism was pushed aside. The local French authorities placed an embargo
on coelacanth specimens from the Comoros, allowing only French scientists
to work on them. They even went to the extent of placing injunctions on
specimens that they donated to various museums around the world, allowing
them to be used strictly for display purposes only and very definitely not
for scientific research. So research on the biology and physiology of the
coelacanth was severely stifled for many years.

Why should so many scientists want to examine Latimeria, and why should
the French have put an embargo on research? Coelacanths, although fish,
possess many features that are shared by the ‘higher’ terrestrial vertebrates,
amphibians, reptiles, and mammals. However, coelacanths are not a missing
link between man and his fishy ancestors, but are one of a variety of fishes
that are very closely related to the first fish with limbs. The group of
fishes thought most likely to be ancestral to amphibians are the Rhipidistia,
which, unfortunately, are extinct. But coelacanths are very closely related
to rhipidistians, hence they may provide some of the best clues the biology
and physiology about the first vertebrates to leave their watery refuge.

And the French embargo? Smith’s venture made the French colonialists
look impotent: the rarest animal on Earth was pinched from under their very
noses. The French must have imagined that if they alone could work on the
beast, then any remaining fame and glory still be to garnered from coelacanths
could go to French scientists and their institutions.

Living Fossil is an enjoyable read, with elements of history, adventure
and tension. It demonstrates that scientists, particularly ichthyologists,
are only human after all. There is a degree of frivolity in its style that
does not distract from the scientific credibility of this work.

Early chapters discuss the personalities associated with the initial
discovery, the culture of the Comores, and the politics and ethics of bounty
hunting. A chapter is devoted to fossil coelacanths, but more importantly,
chapters on habitat, locomotion, physiology and reproduction complete the
picture of the living Latimeria, presenting the reader with a statement
of the current knowledge of this enigmatic fish. All it lacks is a good
colour picture.

Excellent value for money, Living Fossil is entertaining and deserves
to be read by all biologists and palaeontologists, as well as those dreamers
who live in hope that one day a dinosaur will be found lost in the jungles
of some dark continent.

What does the future hold for Latimeria? Thomson’s last chapter carefully
considers this, and it is a bleak prospect. We do not know how many coelacanths
exist in the seas around the Comores, nor if this is their only remaining
habitat.

Unfortunately for Latimeria, there are great economic incentives for
the locals to catch this fish, dead or alive. This comes in the form of
bounty money from aquariums, scientists seeking fresh material and fat cats
wanting to bask in the glory of owning a piece of prehistory. To them I
say, if you want to be famous go and find a Tertiary fossil coelacanth,
and leave this born survivor to live in peace.

David Martill is a lecturer in earth sciences at the Open University,
but will be unemployed after April 1992.

BEFORE you start to read this review in earnest, take a quick look out
of the window. What you are seeing is a world in the middle of a mass extinction
event. On the face of it a mass extinction does not appear to be a dynamic
process; rather slow on a human timescale. On a geological timescale, however,
it is a rapid process, and the aftermath a statistical nightmare in the
fossil record.

Until recently mass extinctions were curious phenomena, palaeontologists
recognised them only in the fossil record, while other researchers showed
little serious interest. A recent possible causal link with extraterrestrial
processes, such as meteorite or comet collisions with the Earth, and the
possibility that such events may occur at regular intervals, perhaps every
26 million years, has attracted the interest of an assortment of scientists,
and fuelled furious debate. The subject is now the stamping ground of astrophysicists,
statisticians, palaeontologists, geochemists and numerous other interested
parties. With so many scientists treading the same patch controversy was
bound to arise; not just because palaeontologists felt their noses put out
of joint, but because there are real problems with the data, and how it
should be interpreted.

The recent interest in mass extinctions, like many scientific discoveries,
came by accident. Researchers, except for a minority of palaeontologists
in America, widely accept that the dinosaurs were extinct by the very end
of the Cretaceous period (now affectionately referred to as the K/T boundary).
That is to say that the last of the dinosaurs roamed the Earth 65 million
years ago. The question as to why they became extinct remained unanswered.
In 1980, Alvarez and others suggested that a meteorite impact may have been
responsible. They came to this conclusion when they discovered high concentrations
of the metal iridium, one of the platinum group of elements, in sediments
deposited at the very end of the Cretaceous.

What they were originally trying to ascertain was the amount of time
represented by the deposit. Iridium enters the Earth from space at a constant
rate in the form of micrometeorites. Therefore the concentration of iridium
should increase when the rate of sedimentation decreased. Alvarez and his
co-workers found that the amount of iridium at the end of the Cretaceous,
if it had entered the sediment at a constant rate, represented more time
than life had been in existence. The only satisfactory way to explain this
superconcentration of iridium was to suggest that a large meteorite had
struck the Earth at the end of the Cretaceous. The controversy that still
rages concerns the aftereffects of this impact.

Donovan’s book is the first to bring together a group of scientists
working independently on the subject of mass extinction. He has aimed, successfully,
to bring a balanced approach to the subject, and not to pander to the sensationalists.
Recent scientific and media attention has concentrated on the K/T event,
but Donovan has carefully assembled a group of authors who are concerned
with extinction events in other parts of the geologic timescale as well
as at the K/T boundary. Mass extinctions have been taking place since life
began. The physical surface of the Earth is an active arena, and mass extinctions
are, it seems, an inevitable fact of life, or rather, of death. Sooner or
later some big volcano is going to blow its top, or a comet come slamming
in from some distant part of the Solar System.

Donovan offers a welcome discussion on what constitutes a mass extinction,
and offers some criteria for recognising one. This is welcome, as the fossil
record is notoriously variable, and its interpretation littered with pitfalls.
Palaeontologists must ask first what the evidence is for a mass extinction.
The evidence comes from fossils not being in rocks – one of the few cases
where negative evidence really counts. This raises a number of problems.
Clearly, a fossil may turn up one day, and suddenly we find our organism
is not extinct after all (the case of the coelacanths is perhaps the best-known
example).

The way in which palaeontologists classify fossils may also cause problems.
Many researchers work on specific sections of the stratigraphic sequence,
say the Triassic, whereas a different worker may study the same organisms,
but from Jurassic rocks. If the Triassic worker is a ‘splitter’, and creates
20 new genera, and the Jurassic worker is a ‘lumper’, creating only five
new genera, then a mass extinction may be recognised at the Triassic/Jurassic
boundary. There is another anthropomorphic factor. Palaeontologists recognised
the Triassic because its red beds dominate deposits in Europe (red clays
and sands laid down in terrestrial environments), whereas marine deposits,
notably clays and limestones, represent the Jurassic. So it seems from the
data in Europe that many terrestrial organisms became extinct at the end
of the Triassic. Clearly, the nature of how we document the fossil record
is important in our interpretation of past events.

Donovan has selected events where palaeontologists are reasonably happy
that they have ironed out, or compensated for vagaries of the fossil record.
The various authors consider a range of organisms, from the spectacular,
such as the mammoths and giant ground sloths, to the obscure Charnia and
Pteridinium – a picture would have been welcome here. The most relevant
chapter in view of the current debate is that by Charles Orth on the geochemistry
of the bio-event horizons. Orth provides a balanced view of the techniques
and rationale employed in the search for an explanation of the K/T event,
but also reviews some other possible impact events. Funnily enough, Orth
skips over what might have been the most important event to date. Apparently
a meteorite of 500 metres in diameter slammed into the Pacific Ocean about
2.3 million years ago. This put some 2 billion tonnes of water into the
stratosphere, possibly triggering glaciation in the northern hemisphere.
We may still be living in the aftermath of that little pebble.

A dinosaur appears on the dust jacket of this book. Publishers believe
that this increases sales by around 25 per cent. For the 25 per cent of
you out there who buy books on the basis of their covers alone, there is
not a single picture of a dinosaur inside.

If I were forced to point out a discrepancy in the book, I would argue
that it needed a chapter on the non-impact theory of extinctions at the
end of the Cretaceous. Perhaps no dissenting author felt inclined to enter
such a lion’s den of opposition. Although the book is short on illustrations,
and some of the chapters are rather dry, Donovan’s book provides the most
important starting point for anyone, lay scientists or professional palaeontologists,
with an interest in death, doom and destruction.