What Is Evolution?

What Is Evolution?

5:08pm Apr 17, 2015
Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com).

SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.

The theory of evolution describes the process by which species change over many generations. Basically, an organism is born with a mutation that gives it an advantage for survival. The trait gets passed down until the descendants out-compete or diverge from the original species. We don’t usually get to witness this gradual change with our own eyes. But there are some ways we can see evolution in action.

There are a whole bunch of things you can look at that show you that evolution is happening very slowly, in many cases, but in the modern world. If you give a bunch of bacteria antibiotics, only the strongest ones are going to be able to fight it off, and then you end up with strains that are no longer sensitive to this medicine you’ve applied. You can do what Darwin did and see a whole bunch of finches that look different from other finches and try to figure out how they’ve adapted to the absence of predators.

That’s Dave Dobson, Professor of Geology and Earth Sciences at Guilford College in Greensboro. Evolution by natural selection takes place over many many generations. And if you’re not a microbe, it happens slowly over great spans of time. So, how do you observe something like that?

If you’re willing to look you can see that history of evolution written very clearly in the fossil record. That covers many, many different evolutionary changes. If you look at the history of lobe-finned fish gradually adapting to life on land, in the last 10 or 20 years we’ve found organisms at all sort of steps along the way that show that gradual transition from shallow-water sturdy fish to kind of cylindrical thing that can flop around on land with legs, to something that’s much more adapted with nostrils and jaws and all that kind of stuff.

To a scientist, if something is a theory it is strongly supported by evidence, and unable to be disproven. We can see the complexity of life progress through the fossil record, and animals from different time periods are never found mysteriously out of order. Even genetic data, when available, matches the fossil record. If these things weren’t true, we would need to rethink the theory of evolution.

Trilobites lived from the Cambrian, the beginning of the Paleozoic, the time when we saw lots of organisms with hard parts and shells, the diverse animal forms, until the Permian, which is the end of the Paleozoic, just before dinosaurs showed up, So you’re never going to find a trilobite with a dinosaur because they didn’t live at the same time.

Biostratigraphy is the method of using known fossils or groups of fossils to put a time period on a rock layer.

The fossil record is a lot like a family photo album, if you pick a random one off the shelf and you see “Oh, that’s when we had Scruffles the hamster,” but we only had Scruffles the hamster in 1995 so this picture has to be from 1995. So the more we know about the history of life, the more we can find individual fossils or groups of fossils and say this must come from this exact time period. There’s a limit to the fossil record, it’s incomplete, and we don’t find nearly as many fossils as there were organisms. But, even the ones we can find and the ones we can interpret show just a rich diversity of fossil forms and transitions all the way through.

You and I are primates. It can be hard to believe for some people, but we do share a common ancestor with other apes.

We did not come from existing monkeys, we came from some ancestor that also gave rise to chimps and gorillas and our nearest relatives. If you went back five million years you would’ve had a population of organisms that are the parent ancestors to us and to modern chimpanzees. If you went back to where your group was merged then there wouldn’t be any difference necessarily between your great, great, great, great ancestor and a chimpanzee’s great, great, great ancestor.

What makes us so special?

Technology can take us places that our genes can’t, and that’s been one of the reasons why the human species has been so interesting, is that capability for complex thought and for invention, one that we see in our near relatives. Chimpanzees make tools and have fights and cheat on their spouses and all the kinds of things that we do, we’re not that different from those populations that we’re closely related to. We’re neat, but we’re not that special - except that we are all us . . . and we have that to deal with too.

This Time Round, the theme music for SciWorks Radio, appears as a generous contribution by the band Storyman and courtesy of UFOmusic.com. 

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