Are Humans Still Evolving? Probably Not

Or at least not by natural selection. A few weeks ago Alan Baxter told me about an article (EDIT: found it here) that speculated that humans would evolve to cope with a high-nutrition western diet and not develop the associated diseases. I'm all for speculation but I think this is way off. There are some pieces in mainstream media about the future of human evolution, but a lot of them seem to promote common misunderstandings of natural selection.

Natural selection is a very punishing force. It works best (operating quickly and creating the most efficient adaptations) when:

• Pressure from the environment is high (ie. most organisms die before they reproduce; from starvation, disease or being torn to shreds). If there's enough food and safety to go around, organisms with adaptive mutations have no advantage since everyone will reproduce.
• Organisms are very actively working to have as many descendants as possible. For evolution by natural selection, an adaptation must usually cause (or at least be linked to) those who have it creating more descendants. Without this, an adaptation will not spread through the population over time.

I think these 2 things are virtually absent in the human world today. Even our biggest killers like cancer and heart disease usually strike after the age most people have children. Hence some mythical cancer immunity is of great benefit to a person but it will not cause them to have more children. And of course these days reproduction is not the only game in town. Culture, social/economic circumstances and personal decisions shape how people reproduce, not genes. So even if an adaptation gives some people the chance to have more children, if they choose not to for other reasons then the population can't evolve.

Here are links, some agreeing, some disagreeing. I've thought of potential objections:

• Aah, but what about the third world? -- The truth is the concept of the third world is largely meaningless nowadays. See this great site for more details (complete with animations!). The gap is closing fast, and we have every reason to believe that in 100 years there will be the same lack of environmental pressure throughout the world. If however the situation in many countries worsens significantly and stays much worse than today for say 30,000 years, there is the possibility of evolution.
• What about pandemics and outbreaks? -- True, a pandemic might select for traits like immunity. It is thought the Black Death selected for many immunities in Europeans (that those in the Americas didn't have, hence massive deaths when the Europeans came). However even then, it's a one-off case, resulting in one evolutionary step. We need many thousands to evolve truly significant changes.
• What about religious fundamentalism? They tend to have more children, their genes will spread. -- An interesting idea. The most probable way homo sapiens can diverge is if there are social groups that don't interbreed. However such divisions must again last for tens of thousands of years -- it would be a very pessimistic view of society where we have a class system for so long (plus it must be MUCH more stratified than in the least egalitarian places today).
• What about evolution by a method other than natural selection? -- This is true, we can still evolve by genetic drift, sexual selection, and even selection by memes. Again, these need to persist for a VERY long time though, current experience is that they don't. But these are our best "hope" for biological evolution.

Of course I say hope with sarcasm. Note the objections above -- the only situations where evolution by natural selection can occur are truly horrible scenarios. I think this is the strongest evidence that it's a very good thing that natural selection is a thing of the past. Many frauds and liars claim there's a link between accepting evolution and great horrors, since people will seek to "emulate" natural selection. If anything it's the opposite -- those who know how horrible natural selection truly is will active in making the human world conquer this immense cruelty. And if we haven't succeeded already, we're pretty close. EDIT: There may be a point that will murder my argument here, if you can think of it let me know and I'll post it!