Humans soon learnt how to catch ever greater numbers of prey
Predators have roamed the planet for 500 million years. The earliest is
thought to be some type of simple marine organism, a flatworm maybe or type
of crustacean, perhaps a giant shrimp that feasted on ancient trilobites.
Much later came the famous predatory dinosaurs such as T. rex, and later
still large toothed mammals such as sabre toothed cats or modern wolves.
But one or two hundred thousand years ago, the world's most powerful
We lacked big teeth or sharp claws, huge
tentacles or venomous bites. But we had intelligence, and the guile to
produce tools and artificial weapons. And as we became ever better hunters
we started harvesting animals on a great scale.
We wiped out the
passenger pigeon, the dodo, the great herds of North American bison. Last
century we decimated great whale populations. Today the world's fishing
fleets routinely take more fish than scientists say is sustainable, leading
to crashes in cod numbers for example, while people kill more large mammals
in North America than all other causes put together.
But out of our
mass consumption of the world's fauna appears a curious conundrum.
Predators and prey are normally locked in an evolutionary arms race. As
predators evolve to run faster, their prey too is selected to become fleeter
of foot. As predators evolve sharp teeth, herbivores evolve horns for
protection. Some carnivores hunt in packs, so their prey form defensive
But animals don't appear to have evolved defences against us.
Which raises the question why?
Is it that these animals simply
haven't had time to evolve defences, or lack the variation in their genes to
produce them? Or is it to do with the way we hunt them?
questions are raised by Professor Geerat Vermeij of the University of
California at Davies, US, in a scientific paper just published in the
journal Evolution. He has been studying the effects of predators on
evolution for more than thirty years.
"Usually, when new, more
powerful predators evolve or come in from elsewhere, the local species can
often adapt by themselves becoming better defended through a variety of
means; but this option seems to be closed when it comes to the evolution of
humans as super-predators," he tells me.
Even huge blue whales have
become potential prey.
In his paper he investigates why this is so.
First he examines how animals adapt to other non-human predators. He
shows how prey animals consistently, and successfully, evolve certain types
The first is growing big. If you can grow big enough, it
becomes very difficult, even for predators hunting in packs, to tackle you
without injury and bring you down.
Scientific studies have shown that
large terrestrial herbivores are by weight up to ten times bigger than their
largest predators, which can't grow mouths large enough to cope with their
outsized prey. It explains why lions, wolves and orca tend to avoid fit
adult buffalo, moose and whales respectively, targeting more often the weak
and young (which are smaller).
If species can't grow big, then they
evolve other defences, such as the passive armour afforded by shells. As
predators evolved to drill through shells, many prey species evolved to
become toxic. The evolutionary arms race once more. A good example here,
says Prof Vermeij, is the cephalopods, animals including squid and octopi.
Early versions of these animals had armour, but as they were eaten by fish
and toothed whales, they were replaced by lineages that were faster, more
aggressive, venomous or toxic.
But then humans came along.
"The spread of modern humans represents one of the great ecological and
evolutionary transformations in the history of life," Prof Vermeij writes in
We hunted and gathered on land, but soon began exploiting
intertidal zones, taking shellfish and fish. Such intertidal zones were
important food sources for prehistoric human populations living in places as
far and wide as South America, South Africa, California and Oceania.
Boar hunting depicted in the 14th Century. Then we started taking big
animals. When we did the very adaptations that offered protection against
natural predators attracted rather than deterred human hunters. The huge
size of mammals such as bison or whales made them juicy targets for
meat-hungry humans for example.
Other defensive ornaments became
disadvantageous as humans evolved into super-predators. Elephants were
killed for ivory, crabs and lobsters fished for their large meaty claws.
These once advantageous traits became liabilities in the modern,
We didn't just take large species, we also
preferentially harvested out the largest individuals of smaller species, a
problem that persists today.
Prof Vermeij has examined the degree to
which this happens.
He looked at one group of animals, marine
molluscs and echinoderms such as starfish, and surveyed all the scientific
research into how they have been exploited by humans. We select the largest
individuals among 35 of 40 species studied, he discovered.
that size is no longer a refuge. Whereas growing big may have been one
defence against natural predators, it offers no defence against human
Sticking to rocks, as limpets do, is no good either
as humans have invented picks and knives to prise them off.
animals may do better to become toxic instead, and there is evidence that
some marine species have become poisonous to people, either producing their
own toxins, or by harnessing toxins produced by microbes. Reef fish and
crabs are often toxic to people because they contain unpalatable, and
sometimes lethal, dinoflagellates, for example.
attracted rather than deterred human hunters (Ron O'Connor / NPL)
humans have found ways to get around this too. Many toxins need to be
concentrated into organs such as the liver. And humans have learnt to remove
these, to avoid their ill effects.
In short the way humans hunt
appears to be the main factor preventing animals evolving adaptations to
defend themselves from us.
Animals do respond to selective pressures,
even over short time scales, and many species have responded to humans being
super-predators, says Prof Vermeij.
By eliminating large apex
predators, secondary predators have boomed. As cod numbers crashed in the
20th Century, their place was taken by an abundance of shrimp, lobster and
crabs, which in turn feed on marine snails. As a result, these snails may
have evolved thicker shells to protect themselves against these marauding
But we hunt on too grand a scale, with
too much ingenuity, targeting the biggest animals.
"Our arrival and
technological history has engendered an enormous change in the evolution of
most species on Earth," says Prof Vermeij.
In evolutionary terms, we
leave our prey with nowhere to go. They have no way to defend themselves and
simply cannot respond.
And that, says Prof Vermeij, represents a
cataclysmic shift for species on this planet, the implications of which, he
adds, we have barely begun to understand.
February 17, 2012 at 5:17 pm
Homo sapiens is an odd species'. We
like to think of ourselves as the pinnacle of evolution, but that is too
self-congratulating. EXTREMITY of evolution is perhaps more accurate. We are
off to the side. Way off. . . . The human brain is a clever replacement for
If you look at it from an evolutionary point of view, the
human brain is just a different kind of gigantism. If you could take our
minds--the sum of our feelings, thoughts, impulses--and cast them in physical
form, you would gaze upon a collection of sizes and shapes that would make
the dinosaurs positively boring. Einsteins, Ted Bundys, Newtons, Hitlers,
Mozars, Shakespeares, popes, and saints--the range exceeds comprehension.
It's sobering to think that gigantism goeth before a fall.
speaking of dinosaurs in a museum] have been dead--ever since the Cretaceous
period ended at 2:12 P.M. on March 2, seventy million B.C. I give the "exact
time" to illustrate how ludicrously short and preposterously self-centered
our human concept of time is. When you deal with environmental impact and
ecological change, you must think in earth time--the rate at which the planet
ages and changes naturally.
To put us in perspective, let us go
forward seventy million years and see what the fossil record has to say
about Homo sapiens. Straightaway we run into a curious problem: the smallest
increment the fossil record can resolve is about one hundred thousand years;
anything that happens closer together than one hundred thousand years can't
be separated. This means we would be hard-pressed to tell from the fossil
record whether Christ came before or after the computer--or even, for that
matter, whether he came before Neanderthal man, or whether Neanderthal man
came after the nuclear age, which would make a lot of sense.
point is, human civilization has arisen so fast in comparison to the rhythms
of the natural world that it cannot be measured in geological time. IT IS
LIKE A SUBATOMIC FLASH. An alien race arriving in seventy million years
would conclude that we had arrived instantly, perhaps from another planet.
The critical question is, HOW DO YOU CONTROL A FLASH? A greenhouse effect
caused in the last hundred years; a hole in the ozone layer in the past
thirty years; three billion people added to the population since 1950--the
rapidity of these trends is out of all proportion with ecological/geological
change, and we are currently engaged in one of the planet's greatest and
fastest extinctions. It will be indistinguishable from the impact of an
asteroid. We are, in other words, the instruments of extinction.
source: "DIVORCE AMONG THE GULLS-An Uncommon Look At Human Nature" by
William Jordan [Harper Perennial, NY 1991]
2012 at 10:03 pm
Nowhere have I seen the point made so clearly of
this species being like a cancer, a disease, stupidly and oafishly
destroying everything in it's wake, including itself in the long run. Of
course animals cannot adapt or build defenses to bullets and arrows shot out
of nowhere, or traps and cages, etc. All the advantages are brutally taken
by humans, an anti-nature, toxic species placed here among a natural
self-regulating system, going in and raping it, taking its creatures and
putting them in hideous prisons, torturing them, like brainless barbarians.
If suddenly animals all became toxic for us even to touch, that would be a
fantastic solution (as long as good people could keep our present companion
animals till they die that is!)