I think it is quite obvious humans are continuing to evolve, even though all humans belong to only one species, that does not mean we are not evolving. If I could pick only three examples of current human evolution at work, it would be the ability or inability to digest lactose, the mutation to resist infectious disease, and even having blue eyes.
Lactose tolerance is only a recent occurrence in human history within the last 10,000 years humans became able to continue digesting lactose after they were weaned off breastmilk. This trait is far more common in Europe than anywhere else in the world because of their domestication of cows. It would seem that Europeans continued drinking cow’s milk until they quite literally mutated to digest it. Fascinatingly at least three more independent variations of lactose tolerance developed in Africa none of which were from the European line of gene mutation. I wonder if the mutation is so different because East African’s would have been drinking more goat milk or if it was because dairy farming in general was not nearly so prevalent until colonial invasions of Africa? Yet another mutation of this kind happened in New Zealand when sheep farming became the dominant form of animal agriculture in the country. Even stranger to think about is lactose intolerance, which is now considered to be a recessive trait even though as recently as 10,000 years ago lactose tolerance after infancy did not exist in significant populations. Even today ⅔’s of the world’s population do not produce enough lactase in their body to digest lactose after age 5. Today the ability to digest or not-digest lactose as an adult can be determined by a genetic test of which nucleotides are riding on your lactase gene. I think this is a clear cut example of human gene mutation/evolution in which populations who consume tons of dairy mutate to be able to digest it and all other populations with access to more diverse food sources have no need for the higher rates of lactose tolerance and maintain their recessive genetic trait of lactose intolerance.
Infectious diseases continue to break through all the modern “cultural evolution” that humans are so proud of and remind us that we are subject to the selection pressures of nature just like all other specie on Earth. I think this is the most impressive example of biological evolution in action, the genetic mutations to resist diseases. The example cited in our lecture was of resistance to malaria, the same mutation that causes sickle-cell anemia, if only one copy is present confers resistance to malaria, one of the worst diseases still plaguing human populations. I was also thinking of the largest outbreak of Ebola in history that happened not long ago, and how carefully studied were a very small group of people who survived contracting Ebola or were simply not able to contract it in the first place. That was the fascinating part, there are many genes if mutated can confer resistance or protection against Ebola, these mutations are extremely rare in Europe, way more common in Nova Scotia and may be present in at least 15% of the population in Africa. There are even recorded genetic mutations in the genes that code for cholesterol in the body, or delete receptors on lymphocytes or bind and block receptor attachment by HIV, all of these mutations create resistance to contracting HIV/AIDS. For a species that wonders if it is still evolving we certainly have a stunning array of mutations to choose from that can protect us from/or entirely prevent some of the deadliest disease that exist in the world today.
The idea that humans are not evolving simply lacks scientific rigor. I believe there is plenty of genetic evidence of recent and ongoing human evolution. I think of everyone I’ve ever met with blue eyes and that is another evolutionarily-recent genetic mutation in our species. I’m not sure there is even scientific agreement on what the advantage is of that trait but it has obviously persisted in our species as a form of natural selection, which is evolution in action. I think the human genome is evolving very slowly but the mutation of our genes is going very fast, this is a protective trait, like and evolutionary air-bag that I believe will protect humans from any harsh and sudden changes in the environment, giving (at least) some of us the chance to evolve and survive new and unforeseen natural selection pressures from our environment. Although I’d bet we’d have to colonize other planets in order to separate our population enough to develop real separate species of humans, that would be so exciting but it would take quite some time and may not even work like that…