Several interesting articles over at the NY Times.

[Steve Reason]

Here are several interesting articles about evolution (that you might have already read) that I think you might enjoy, if you're into science and all of that. I linked to the first one, and there are several more articles in the "Past Coverage" section towards the bottom of the page. I'm not sure, you might need to sign up to see them.

NY Times science articles about evolution

What I took away from them is just how lucky we are to be here. I've always kind of thought that we were more or less destined to be here (humans, I mean), biologically speaking. But I don't think it's so. Here's a passage from the article From Bacteria to Us: What Went Right When Humans Started to Evolve? about how lucky we are to be here. It also talks about how natural selection isn't the only part of evolution that matters-- which I think some have been lead to believe.


 

"Everybody thinks evolution is natural selection, and that's it," Dr. Lynch said. "But it's just one of several fundamental forces."

In a paper accepted for publication in the journal Molecular Biology and Evolution, Dr. Lynch argues that eukaryotes' complexity may have gotten started by chance.

Natural selection is the spread of genes as a result of their ability to raise the odds of survival and reproduction. But when the peculiar features of eukaryotes first arose as accidental mutations, Dr. Lynch argues, they were probably harmful.

Once an intron was wedged into the middle of a gene, a cell had to be able to recognize its boundaries in order to skip over it when making a protein. Some mutations to the intron made it difficult for the cell to recognize those boundaries. If the cell couldn't edit out the intron, it produced a defective protein. If natural selection had been strong in early eukaryotes, all introns would have been eliminated.

Evolutionary biologists have long recognized that natural selection is a matter of probability, not destiny. Just because a mutated gene raises the odds that an individual will reproduce is not a guarantee that it will spread in a population.

Think about flipping a coin. It has 50 percent chance of coming up heads or tails. If you flipped it twice, you wouldn't be surprised to get two heads. But you would be surprised if you flipped it 1,000 times and got 1,000 heads.


Likewise, natural selection works more effectively as populations get bigger. In small populations, it is not so reliable at spreading beneficial genes and eliminating harmful ones.

When natural selection is weak, genes can become more common simply thanks to chance.

The random spread of genes is known as genetic drift. Dr. Lynch argues that genetic drift is much stronger in eukaryotes than in prokaryotes. Several factors are responsible, including the bigger size of eukaryotes. Even a single eukaryote cell may be 10,000 times as large as the typical bacterium. Far fewer eukaryotes can survive in a given space than prokaryotes, leading to smaller populations of eukaryotes.

Dr. Lynch argues that early eukaryotes experienced strong genetic drift. Their population may have shrunk. Natural selection became weak, and genetic drift became strong. Genes that were slightly harmful to the proto-eukaryotes became widespread.

Although these changes may have been caused by genetic drift, they created opportunity for natural selection to create adaptations. Exons could be spliced to create proteins adapted for different jobs. Genes could be switched on in different places, to help build new organs. Complex multicellular organisms - like humans - could emerge.

Natural selection has produced useful adaptations in eukaryotes. If it hadn't, Dr. Lynch said, "we wouldn't be here."

Prokaryotes never got the chance to evolve this complexity because their populations were so large that natural selection blocked the early stages of its evolution. "There was one lucky lineage that became us eukaryotes," Dr. Lynch said.

[Will]

Evolution is one of the most beautiful things in nature. I consider myself fortunate to understand the basics and appreciate how magnificent it all really is.

Thanks for the articles!