If anyone tells you that there is no real-life proof of evolution, you can tell them this little story about evolution in the lab. It goes something like this:
Biologists were trying to figure out what first caused one-celled creatures to group together and become multi-celled creatures, or, creatures with bodies. One theory was that the molecules that glue cells together first evolved as a way for cells to latch onto other cells in order to consume them and that at some point it became prudent to be bigger so cells just used this glue to bunch up.
So, a chap with the unfortunate name of Martin Borass took an alga that is normally single-celled and let it live in a tank for 1000 generations. It continued to be single-celled. Then, he introduced a predator, a single-celled creature with a flagellum that engulfs other microbes to ingest them. Within 200 generations, the alga responded by becoming a clump of hundreds of cells.
Over time the number of cells dropped to 8 in each clump. Eight turned out to be the optimum number because they were big enough not to be eaten and small enough so that each cell could pick up light to survive. (This all took several years).
Perhaps the most interesting thing was that when the predator was removed from the environment, the alga continued to reproduce and form individuals with 8 cells. Another interesting point is that, since it was so easy to go from one cell to multiple cells in the lab, why didn’t it happen earlier in nature? Well, it turns out that compounds like collagen (the glue) takes a lot of energy to produce, energy derived largely from oxygen. It wasn’t until about a billion years ago that oxygen levels started to rise significantly, and that’s when bodies (muti-celled creatures) began to show up.
But I thought the world was only 4000 years old; how could that happen so long ago?
ReplyDeleteThat's a pretty persuasive argument for evolution (as if we needed one). It's interesting that they didn't devolve with the pretator removed.
war