Be patient with us humans – we're still evolving
Researchers find that humans have changed significantly in just the past 1,500 years or so.
Scientists researching the evolution of earthly life aren't just looking in a rearview mirror. Evolution through natural selection, which has shaped the biological world, is active today. It guides the adaptation of plants and animals to climate change. It affects the way endangered species respond to conservation programs. It is changing the human species in unsuspected ways.
New data on the accumulation of recent mutations in the human genome upends the standard assumption that modern humans have evolved little since they emerged from Africa some 40,000 years ago. Instead, team leader Henry Harpending at the University of Utah in Salt Lake City says the data indicate that "humans are evolving rapidly and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago." He adds, "We aren't the same as people even 1,000 or 2,000 years ago."
Professor Harpending and colleagues at several other universities are tracking the occurrence of simple point mutations along the genomes of specific individuals. The data include 3.9 million of these mutations in 270 people from Han Chinese, Japanese, African Yoruba tribe, and northern European populations. The Europeans are represented largely by Utah Mormons.
These are limited data. Yet, as a first cut at tracking contemporary human evolution, they indicate a surprising trend. The human groups on different continents are moving away from each other genetically, not mixing together. One of the team's key findings, reported last month in the online Proceedings of the National Academy of Sciences, is that 7 percent of human genes are undergoing rapid evolution.
Harpending explains that this is to be expected, since there has been relatively little gene flow between these groups since they dispersed out of Africa. Any genetic changes favored by the new environments would spread rapidly within each dispersal group. What these changes mean for humanity is not clear. Also, globalization may reverse the tendency for populations on different continents to drift apart genetically.
Meanwhile, last November, an international group of fisheries scientists warned in the journal Science that conservationists should take account of evolutionary effects in efforts to save endangered species. Fisheries management is a striking case in point. It's obvious that human pressure on fish stocks has an overwhelming influence. What has not been so obvious to fisheries managers are the evolutionary responses of fish species to this pressure. It can change significant traits, such as size and age of sexual maturity.
Such changes and their side effects may be undesirable. The group notes that such "fisheries-induced evolution may also be slow to reverse or even irreversible" when fishing bans allow a fishery to recover. Fisheries management – indeed, all endangered species management – needs planning that takes account of evolutionary implications. The group recommends that planners make an evolutionary impact assessment as well as an ecological impact assessment when management programs are designed.
The human genome research and the fisheries group's warning both emphasize an important point. We can't take present-day plant, animal, or human genomes for granted. The genetics of the biological world, including human genetics, may be changing rapidly in unsuspected ways.