February 07, 2019
January 17, 2018
1. Citation please. Author and title.
2. There’s no such thing as “devolving.” Natural selection doesn’t care if, for example we swim, slither, crawl, walk on four legs, walk on two legs with our knuckles scraping the ground, or walk on two legs with arms too short to touch the ground. Natural selection cares whether the way we get around enables us to survive and reproduce in our current environment. Going from two-leg walking back to swimming isn’t “devolving.” It’s just “evolving.”
3. The only known beneficial “genetic error” is sickle cell? Snort. In the recessive condition, SC protects against malaria, just like you said. But in the recessive condition, Tay-Sachs may help protect against TB (that one’s still not decided yet though). And in the recessive condition, cystic fibrosis is protective against cholera, typhoid fever, and possibly asthma. In the dominant condition, these conditions are disabling, quickly and horribly fatal, and disabling and life-shortening, respectively. There is also a “genetic error” in the gene that produces CCR5, a protein receptor on the surface of white blood cells. People homozygous for this “error” seem to have a greater susceptibility to West Nile Virus, but they are completely immune to many strains of HIV.
4. And about those “genetic errors.” (By which I assume you mean DNA transcription errors that happen during the formation of the reproductive cells and thence are passed to the next generation – the ONLY kind of errors that have any relevance whatsoever to evolution.) Well, “genetic errors” of all sorts happen all the time. Some are harmful. Most have no effect. A few are beneficial to continued survival, or greater reproduction, or both. An individual with a beneficial “error” will tend to leave more offspring, and if the “error” is transmissible to the next generation, some or all of the offspring will also have the “error.” If this cycle continues through the generations, eventually the beneficial “error” will become more prevalent in the population. Ladies and Gentlemen, I give you Evolution by Natural Selection. Give ‘er a round of applause.
5. Perhaps your point was that we’re all “devolving” into sicker, more pathetic versions of ourselves, and eventually at some point it might even get so bad that some future generation will dissolve into a puddle of inert goo because, darn it, our genes got too riddled with errors. If that’s ever happened in 3.5-ish billion years of evolution on this planet, I’d love to hear about it. Generally, extinction happens because environmental factors change, and the mechanisms of natural selection don’t have time to produce new forms or behaviors that can survive in the new environment. They certainly die trying though. Extinction does not happen because one’s own genome implodes from within and self-destructs the species. If humans became the first, it’d certainly be an interesting process to observe.
6. Try the Bill Nye the Science Guy episode on evolution. I’m not being sarcastic. It’s a pretty good introduction to the subject.
@Everyone else – pardon my rambling.
September 25, 2019