(Evolution for dummies. I wrote and posted this to another site many many years ago. This rant is still a useful read for folks that don't fully grasp what evolution is really all about)
Recently an “Intelligent Design” believer asked if evolution had any proof and made mention of the scarcity of hominid fossils. What follows below is my answer... an attempt to explain what evolution is and is not, and how it provides a complete and satisfying explanation for the current state of life on our planet. Even if evolution is not an explanation we might desire, evolution is the explanation that is true.
Coconut Crabs ( http://en.wikipedia.org/wiki/Coconut_crabs ): The adult coconut crab lives on land and has a cheesy primitive lung in its rear end. They thrive on islands scattered across the South Pacific Islands where no humans, and probably no mammals or rats live. Why? Because unlike mammals, the crab larva can get tossed there by storm water. Mammals (until very very recently) had no way to cross the water so the crabs and birds have these islands to themselves. Why don't the crabs live on the Eurasian land mass? Simple, they can not compete. Their cheesy lungs and exoskeleton are no match for rats, bears, and people. So how come they have these primitive lungs? Because otherwise they could not live on the silly island. Life is always trying to find a safe home for itself, and the crabs apparently had the best shot at those islands so off they went.
Can Genesis explain why God would plop a crab with a crappy lung in a swiss cheese pattern across the south pacific? Natural selection explains why the crabs are there, they provide a fine example of parallel evolution (lungs), transitional forms (primitive lungs, not as good as ours). Darwin explained why critters look and act the way they do and why they have the capabilities they have. And it is not an accident, it happens in nice neat steps to meet the arbitrary needs of prehistory. Why didn't God give the crabs gorgeous muscle powered lungs like ours? lungs that can cope with dry air? Why? because evolution does not work that way. Critters gotta crawl before they can walk. With our deep 500 million year ancestry we are many many steps ahead of the silly coconut crabs. But they could swim there... so there they are.
Example #2: Platypus and Spiny Anteater . Those egg laying mammals are real odd balls. Why there? Why so odd? Why only two species? Genesis won't tell you but evolution will. What happens when big placental mammals compete for an environmental niche with big egg laying creatures? Placental mammals (and humans) rule! Why? Egg layers lay lots of eggs while a placental mammals spits out a single baby or litter.... but by definition a placental Mom protects her babies with her life until they are born, and probably likes a good breakfast of eggs whenever the opportunity presents itself... Little critters: eggs. Big critters: live young. Case in point: big sharks, live young, little sharks, eggs. Another case of parallel evolution. Why? Because Darwin is Destiny. Not random at all. Big critters usually have live young because big critters need to have live young to compete effectively.
Anyway, back to the Platypus and Spiny Anteater . Once upon a time, Australia was crawling with a full spectrum of different egg laying mammal species. Then along came the Marsupials. Another pesky land bridge mixed two competing evolution lines and one emerged the victor. All the egg layers disappeared and the marsupials took their place. How do we know? That pesky physical evidence. Why did God stick rocks that look like egg laying mammals in certain strata of Australia with no Marsupials in the same strata? Is the God of Abraham into deception and conspiracies? Evolution is fact backed by tons of physical evidence. Anyway, back to the Monotremes (egg laying mammals). All but two species went extinct. But which two survived? Weird two. Why weird and not boring leaf or grass eating egg layers? I think the Marsupial Otter that lived in burrows by the water got beaten by the Platypus and its poison barbs. Being a small burrow dweller also means eggs are not much of a disadvantage. There may not have been a Marsupial Otter. And the Platypus was good enough at its job to compete for and keep its slot. But egg laying grazers? The big kangaroos ate their lunch. That and their eggs.
Need another example? Terror Birds that ate deer were the top predator in South America until 2 million years ago. That's like 50 million years after the Dinosaur disappeared. Why are they gone? Evolution has the answer: Cats. Cats beat the egg laying terror birds at their own game. But the big Cats could not walk down to South America until 2 million years ago. Its not "accidental" evolution. Cats eat birds, everybody knows that. :).
One last example of extinction and that pesky fossil evidence. Until 10 thousand years ago, North and South America was crawling with a variety of large mammal species that puts the Africa of Today to shame. Why did they all go extinct and what took their place? Answer: Placental mammals may terrorize terror birds, but humans terrorize the whole damned planet from top to bottom. Even stone age humans with nothing but sticks and fire. Some facts (backed by physical evidence): Africa lost 30% of her large animal species over the last 100k years.
The Americas, Europe, Asia, Australia, New Zealand, Hawaii etc all lost 70% of their largest animal species. When? In every case when Humans hit the beach. At different times for different places. Why only 30% in Africa? Co-evolution. The Animals in Africa where there while hominids came into their own. The had a whole lot more time to adapt and hang on while hominids went from ape to modern man. Where did all the other transitional hominids go? If the ice age didn't kill them, I'm sure our ancestors did. Why is there greater genetic variety in the various African human strains than in the rest of the world combined? ( More of that pesky physical evidence. ) Because Africa is where we evolved silly. A few foot loose and fancy free folk wandered out of Africa to spawn and become the Asian and Anglo strains.
The Americas, Europe, Asia, Australia, New Zealand, Hawaii etc all lost 70% of their largest animal species. When? In every case when Humans hit the beach. At different times for different places. Why only 30% in Africa? Co-evolution. The Animals in Africa where there while hominids came into their own. The had a whole lot more time to adapt and hang on while hominids went from ape to modern man. Where did all the other transitional hominids go? If the ice age didn't kill them, I'm sure our ancestors did. Why is there greater genetic variety in the various African human strains than in the rest of the world combined? ( More of that pesky physical evidence. ) Because Africa is where we evolved silly. A few foot loose and fancy free folk wandered out of Africa to spawn and become the Asian and Anglo strains.
Ok, one last example: "Genesis is literal fact" folk are obsessed with eyes. Surely some deity "designed" them? Nope. The fossils show that eyes were an early innovation in both endo and exo-skeletal animals. Way back when dry land was devoid of life. Darwin is destiny. Eyes are important. The earliest critters had them because if they didn't they would have been dead. duh. The Nautilus has an open eye cavity and no lens. If eyes are important, why did the nautilus get short changed? Because it travels hundred of vertical feet in the ocean generating a pressure delta of several hundred PSI that would squish any closed eye. The vertical migration must offset the benefit of a closed eye ball. Its not random. Its Destiny. The Nautilus has what it needs, the best it can get. Today we can find fish with light sensitive spots on their skin.... not even good enough to be called a primitive eyes, but a precursor to an eye none the less.... that pesky parallel evolution and intermediate form thing again. Anyway, for more on eyes, read this: http://en.wikipedia.org/wiki/Evolution_of_the_eye, they say it in far more elaborate detail than I can.
The story of evolution is far richer and full of physical evidence than Genesis. I've barely scratched the surface of that story here. And its a very interesting story. If you are hungry for more, but reading is not your thing, I recommend the BBC series "Walking with Monsters", quite entertaining.
Where is the proof? The earth is full of proof all around the globe, both in the life above and the fossils below. Evolution is fact, backed by genetics, backed by fossils, backed by the reality of the creatures in the living world. To believe otherwise Today requires willful ignorance.
Darwin is prehistory. Genesis is history.
Thanks for listening,
PS: Darwin is destiny, and sex is the engine that makes it go. That is why every species on the planet likes to mix up the genetics with creatures of its kind. Anything else is a literal dead end.... so purely asexual creatures can not exist. Our Destiny is for all creatures, great and small, to have sex.
PPS: In addition to genetics, there are many other places where its principals can be applied. Places that challenge our ability to steer our own destiny. A challenge I hope we are up to beating: The evolution of human ideas or memes. This includes governance, religion, human technology, and governing institutions, including financial systems. They adapt, evolve, mutate, have children, and die... all within the space of humanities collective brains... passing from human to human via the spoken and written word.
One example: Television as Entertainment. Is it maladaptive? If so... over a few thousand years, any genetics that steer people away from it will get promoted and any that steer people towards the couch will become extinct. It is simple destiny. Same goes for online existence.... but only if the human race can adapt before the changing environment kills us all off.... biological evolution is much slower than the current rate of change in both our technology and the living world we need to survive physically.
This rant was and is meant to hint as to why i we need to pay attention to the world we are creating for ourselves and our children. Their survival will require an environment where they are still the owner and apex consumer.
