I think the easiest way to grasp evolution is still Darwin's original theory. It's just two observations and a postulate.

Observation one; organisms produce more offspring than can be supported by the environment. That might not sound right to you, but if you look into it, you'll find it's accurate.

Observation two; all organisms exhibit variations from each other which can be passed to offspring. All right, some things clone themselves, but that's a refinement of the observation, it doesn't obviate it.

Postulate; over time, those variations which tend to increase survival and reproduction rates will come to dominate a given population.

That's it. Everything else stems from that.

Originally posted by Astyanax
I would not necessarily come to this conclusion. The incidence of carcinogens and other dangerous substances in urban environments has been high since Roman times at least, and almost certainly earlier. Indeed, some mediaeval and early modern environments were probably more toxic than their equivalents today. People cooked in lead pots, ate mercury to cure their diseases and did all kinds of crazy things.

The low incidence of cancer in former times is more likely to do with the fact that cancer is mainly a disease of late maturity and old age, and until fairly recently most people did not live long enough to experience it.

Or simply that people back in those days didn't know what cancer was and could only describe such diseases as witchcraft. Also, while we have the capabilities to detect cancer in the body, such as those that would develop in the intestines and kidney for eating and drinking lead, mercury, etc, while those that lived back then couldn't and thus didn't document it. Doing autopsies is a fairly new thing.

Originally posted by jiggerj
Evolution has yet to be describe to me in a way that sticks in my head. Can someone explain IN LAYMAN'S TERMS what I am about to ask.

In evolution I would expect to find many samples of a species with gradual changes that has taken place over millions of years. In the image below, there are three skulls of Australopithecus afarensis (that I manipulated). The first specimen lived 3 million years ago (I don't know the exact years, so I just wrote 3 million). This one has a very bony brow.

The second one lived 2 million years ago. Through the process of evolution, as this species moved closer and closer to becoming human, I would expect to find subtle differences, but this creature would still be called Australopithecus afarensis, only with a less severe bony brow.

Then the one that lived only a million years ago I would expect to find the bony brow gone, but still considered Australopithecus afarensis.

Is this, in fact, what science is finding? Because if we aren't finding subtle differences in any given species, how can it be considered evolution?

How can these identical (in every way) skulls be millions of years apart.
Look at the white bits connecting theactual remains - completely identical, the teeth are identical as well.
One skull photographed 3 times and labelled as coming from 3 different periods in time.
My opinion - epic fail.

Originally posted by Sailor Sam

Originally posted by jiggerj
Evolution has yet to be describe to me in a way that sticks in my head. Can someone explain IN LAYMAN'S TERMS what I am about to ask.

In evolution I would expect to find many samples of a species with gradual changes that has taken place over millions of years. In the image below, there are three skulls of Australopithecus afarensis (that I manipulated). The first specimen lived 3 million years ago (I don't know the exact years, so I just wrote 3 million). This one has a very bony brow.

The second one lived 2 million years ago. Through the process of evolution, as this species moved closer and closer to becoming human, I would expect to find subtle differences, but this creature would still be called Australopithecus afarensis, only with a less severe bony brow.

Then the one that lived only a million years ago I would expect to find the bony brow gone, but still considered Australopithecus afarensis.

Is this, in fact, what science is finding? Because if we aren't finding subtle differences in any given species, how can it be considered evolution?

How can these identical (in every way) skulls be millions of years apart.
Look at the white bits connecting theactual remains - completely identical, the teeth are identical as well.
One skull photographed 3 times and labelled as coming from 3 different periods in time.
My opinion - epic fail.

Holy crap! That's good. Epic fail. No reason for you to return here. Wow!

Originally posted by Astyanax

Species don't turn into other species overnight.

That's exactly my point. But it seems that what we're seeing is how one species suddenly dies off and a new species suddenly appears around the same time. We're not seeing gradual changes within a specific species. And, that bothers me.

Another example of this is the introduction of peregrine falcons to places where the raptors were not previously found. Pigeons are cliff dwelling birds. They are prey for peregrines. Pretty soon the lighter colored pigeons at Devil's Tower in Wyoming were a thing of the past. They were just too easy to pick off it seems. The rock is dark and from above a white dot moving over dark rocks is pretty easy to track.

Light and dark pigeons are of course the same species, but the sudden introduction of a skilled predator has altered the gene pool of pigeons in at least one place on Earth.

Originally posted by jiggerj

Originally posted by Astyanax

Species don't turn into other species overnight.

That's exactly my point. But it seems that what we're seeing is how one species suddenly dies off and a new species suddenly appears around the same time. We're not seeing gradual changes within a specific species. And, that bothers me.

Really? Do you look identical to every other person around you? And if you want to take it even further, compare an asian, an african, a european and an eskimo, and tell me they look identical?

Originally posted by Thain Esh Kelch

Originally posted by jiggerj

Originally posted by Astyanax

Species don't turn into other species overnight.

That's exactly my point. But it seems that what we're seeing is how one species suddenly dies off and a new species suddenly appears around the same time. We're not seeing gradual changes within a specific species. And, that bothers me.

Really? Do you look identical to every other person around you? And if you want to take it even further, compare an asian, an african, a european and an eskimo, and tell me they look identical?

That's a very good point. Problem is, we are all still categorized as Homo Sapiens. What I gather from the comments in this thread, whenever our primitive ancestors evolved even in the slightest, they were re-categorized and re-named.

Originally posted by jiggerj
How do these sub-species come about? I imagine that a tribe of one species splits up. Half of them stay where they are and never change. The other half goes off to face adversities in a new environment which causes them to evolve in certain ways in order to survive. Then that tribe splits up, and so on and so on...creating thousands of branches and sub-species.

Under this premise how could EVERY SINGLE branch die out and leave only us here today? Doesn't that seem highly improbable? Not only improbable, but for evolution to have worked this way it would have taken (in my opinion) billions of years.

You are correct in the first paragraph, but also interbreeding takes place among many sub species, so the genes split up and change, but then come back together thousands to millions of years later increasing genetic diversity.

The extinction of other intelligent hominids on earth is a mystery right now. Homo sapiens being the only intelligent beings, is relatively new, however. Just 20,000 years ago we shared the planet with several different other hominids and subspecies. Perhaps a natural disaster wiped most of them out. It may have had to do with the end of the last ice age or an impact event. Maybe homo sapiens killed the others off. We know sapiens and neanderthalensis bred together, as well as Denisovans and another mystery species. If you look in nature, there are many more sub species, but a line dies out when a disaster happens and they cannot adapt. For whatever we, we did while the rest perished. It could have been our location or numerous other factors.

Evolution and the rate of change is dictated by the environment. If a creature is well adapted there is no need for change. Sharks are a great example. They predate dinosaurs by like 200 million years. Yet, white sharks are still here and almost exactly the same, just a bit smaller.

Also that skull picture is obviously photo shopped. I don't know if that was intentional to show what happened, or what, but it's obviously not 3 skull samples separated by millions of years. I didn't even think they had more than 1 skull sample of afarensis.

Originally posted by Barcs

Also that skull picture is obviously photo shopped. I don't know if that was intentional to show what happened, or what, but it's obviously not 3 skull samples separated by millions of years. I didn't even think they had more than 1 skull sample of afarensis.

edit on 31-8-2012 by Barcs because: (no reason given)

Hmmm, you're the second I know of to miss what I wrote in the OP. I wrote: In the image below, there are three skulls of Australopithecus afarensis ***(that I manipulated)***.

I did this to explain what I would have expected to see from evolution.

Your claim is not as clear to others as you seem to think it is.

So in this case you contrived a situation that you think would be important. Why not use 3 different real skulls and stick to the real world?