Juan Enriquez writes of rapid ongoing evolution. Are we current modern humans a transitional species? Where would we look for the beginnings of the next species?
The selection event is going to have to be brutal - right now the expansion of genetic variation within the pool is maximized, possibly even in a theoretical sense for this size of land vertebrate, and the gene pool is unusually well blended - almost no isolated subpopulations, even on a planetary scale. To get a new species would normally require culling and/or isolation. Let's hope that's a long way away, time and space. Loss of the Earth's UV and solar wind protection might give multiple advantages to dark skinned people living along the coast at high latitudes.
If other modified human will appear we will correct their appearance by using surgery, or we will sterilize them .
We've got people of Nordic descent living happily and safely in the tropics (thanks to of the invention of sunscreen, much less clothing), and people of African descent living happily in the Arctic zone (thanks to the invention of vitamin supplements). It's unlikely that a significant portion of the population is going to die as a direct result of an increase in sunshine. If it happens it will be due to the drowning of the cities (virtually all of them were built on the shores of oceans, seas, rivers and lakes because before the Industrial Revolution the fastest way to travel and ship goods was by boat) and the need to rebuild them ALL about 25 miles inland. More importantly, we'll need to adapt our agriculture to the new climate (on SMALLER landmasses!) and while we're doing that, a lot of people will die of starvation. Skin color will be a minor issue.
You underestimate the effects of a loss of the current levels of UV and solar wind protection - either of which are possible with changes in the earth's magnetic field and/or industrial pollution levels. Vitamin D is available from seafood and other diet, UV and solar wind protection is not. So the advantages of high latitude living would be available to dark skinned people, while no such compensation would be available to light skinned people at the lower latitudes. Living "happily and safely" is one thing. Reproducing at competitive levels over the long haul is another. A 1% advantage in repro rate would be overwhelming in Darwinian terms - although recessive traits such as light skin would probably survive among a large enough breeding group (as red hair does among black people in the US now), they would be unlikely to persist as characteristics of significant populations.
How much of your daylight hours do you spend out in the sun? For me it's a few five-minute walks from my car (or other vehicle such as the subway) to my home, office, store or other haven from the sunlight. My worst exposure occurs every couple of weeks during the growing season, when I have to spend two hours on the ride-on mower to keep our two-acre lawn in shape. I bite the bullet and wear long sleeves, long pants, gloves and a wide-brimmed hat, and I have yet to acquire more than a barely visible darkening of my extremely white skin. It's a little uncomfortable to be out in the warm weather with all those clothes on, but I keep the mower in high gear so I get a reasonable breeze. Sorry, I don't understand your point. If the average skin color of the human race darkens over the centuries, how can that possibly be important??? Genetics is now a rather mature technology, and it turns out that skin color is determined by a rather small number of genes that apparently have virtually no other function. It's inconceivable that civilization and progress will be affected significantly by our descendants being darker than us.
If my understanding s correct, lighter skin color is more efficient in processing vitamin d from sunlight.........and, we got those genes from homo-sapiens-neanderthalensis. (wild guess du jour) In the higher latitudes not only do we get less sunlight, but we stay covered up for much of the year, so only small amounts of exposed skin have to make all of the vitamin d that we need to stay healthy. If that is true, and epigenetics is a reasonable hypothesis, then descendants of higher latitude people should stay very fair skinned. One wonders, would using tanning beds change this?
Many foods are supplemented with Vitamin D, and if that's not enough, you can buy it in tablet form. But as I explain below, light-skinned people have very little sunlight-blocking melanin in our skin, so even in arctic and subarctic latitudes our bodies generate enough Vitamin D to stay healthy. Re-read my previous remark. Vitamin D is simply not an issue. Our entire post-industrial civilization would have to collapse before we'd start dying from Vitamin D deficiency, but if that actually happens, Vitamin D will be the least of our worries. And yes, you're correct about skin color and Vitamin D. Dark skin is dark precisely because it has a much larger concentration of melanin than light skin. Melanin is the pigment that causes skin to appear dark, and also blocks out a lot of sunlight. This allows dark-skinned people to walk around with bare skin in bright sunlight without worrying about sunburn. The down-side of this is that by blocking the sunlight, it greatly reduces the ability of dark-skinned people to generate adequate levels of Vitamin D in places where the sunlight is not as bright as in the tropics. They're the ones who have to take Vitamin D supplements if they're working in the Arctic region.
Long ago and far away, when I was in the army, me(blond and blue) another light skinned "white guy" with dark hair and brown eyes, a dark Albanian Greek, and a black guy went to nags head to go surfing (storms coming and the waves were high). When the weekend ended, the 2 with the worst sunburns were the black man, and the dark Greek. (You couldn't see it on the black guy, but he sure felt it.) They too thought that dark skin was a protectant, and................they wuz wrong. 15 gallons of vinegar in the tub, and we took turns soaking. Nobody leaned back into the seats for the ride back..............
