Originally posted by AshleyD
Why do we have animals that seemingly have no real defense mechanism compared to those who do? Rabbits, mice, gerbils, etc. Why don't we all have
some sort of almost indestructible defense mechanism through natural selection?
Man has intellect as our strength but put us in the ring with a shark, lion, or bear with only physical strength and we're basically screwed. Why
don't we all have quills, fangs, claws, wings, venom, etc.? Hopefully someone can answer this logically.
Hi, AshleyD. Congratulations on your appointment.
As SamuraiDrifter pointed out, evolution isn't directed towards continuous improvement. It just looks that way sometimes, and the reason it looks
that way is that natural selection can turn evolution into an arms race - between predator and prey, parasite and host and even between males and
females. New offensive capabilities evolve corresponding defences, which can only be overcome by evolving still other offensive capabilities... and so
it goes.
But that doesn't answer the question.
Here's a simple answer. Are we really defenseless? As you say, an individual man or woman is unlikely to last long in a physical contest with an
individual lion or bear. But evolution isn't about preserving individuals; it's about preserving
genes. And you have to admit that our
natural offensive and defensive capabilities are currently doing a much better job of saving and replicating our genes than bears' or lions' do
theirs.
That leads us to the second answer. If nature's law is eat and be eaten, then it is obvious that all species need defences against other species. The
question to ask is, what constitutes a defence. Fearsome teeth, tusks, deadly claws, impenetrable armour... well, they're pretty obvious ones. But an
equally good defence is running away, and less costly in energy terms (the price of evolution's benefits is paid in energy) to develop and maintain.
Unless you're a predator that needs teeth or claws to get your dinner, it's often better to be fleet of fin, foot or wing, or simply good at
dodging.
But even running away is beyond the capacity of one entire kingdom of life: the plants. Rooted, slow-living, plants ain't going anywhere. But just
look at the defences they've evolved! They have
Animalia* beaten hollow when it comes to defending themselves. In fact, many of them
have incorporated being eaten into their reproductive mechanism: they rely on insects to have their sex for them and on birds and mammals to spread
their seed abroad. They've done this by turning their reproductive organs and offspring into the most attractive and delicious parts of themselves,
so 'predators' will come along, help themselves and leave the rest of the plant alone to grow more flowers and fruit, to propagate its genes another
season.
Nature's defensive strategies are legion. Think of skunks and stink-bugs; leaf-insects, chameleons and false coral snakes; stonefish and
poison-toads; hermit crabs and rhinoceroses; catnip and cannabis; redcap mushrooms and deadly nightshade. Think of the bacteria, whose strength is in
sheer numbers. I could go on and on. The thing these species -
all species - have in common is that they exist to protect and procreate
replicating molecules - genes - and not themselves.
I hope this explanation was satisfactory.
*Just using the old Linnean classifications for fun.