The other day, BBC Radio 4 presented a half-hour show hosted by Adam Rutherford: “Human evolution versus cultural evolution,” the first of a two-part series called “In our own image: evolving humanity”. You can hear the show at the link, and I understand it will be up for a week.
The show features evolutionary luminaries discussing the role of genetic versus cultural evolution in the formation of our own species: these talking heads include Steve Jones, Steve Pinker, Kevin Laland, Steve Stearns, and my own Chicago colleague Anna di Rienzo.
If you’ve been following this website regularly, you won’t learn a lot that is new, but you may want to listen if you’re not up to speed on the question of whether and how much humans are still evolving, which is the topic of this show.
The participants have different takes. Most say “yes,” though Steve Jones, as always, claims that both the evidence for and the scope of genetic evolution in modern Homo sapiens is limited. He argues that since our divergence for the lineage that led to modern chimpanzees, human ancestors have evolved more slowly than those of chimps, and that the evolutionary changes in our ancestry mostly involve losses (e.g., hair). That, of course, neglects the tremendous cognitive gain that we’ve experienced. Jones also argues that the opportunity for selection, which involves variation in both longevity and offspring number (“reproductive success”), has also decreased drastically due to improvements in health care and sanitation.
As I’ve discussed before, Steve Stearns and his colleagues have argued otherwise using the long-term data from the Framingham Heart Study. Contrary to Jones, they claim that there is still sufficient variation among couples in offspring number to lead to substantial selection on health-related traits.
Steve Pinker talks about cultural versus genetic evolution; it may surprise some that he’s not a diehard evolutionary psychologist here, and argues that traits like music-making might not have been the direct object of selection, but rather evolutionary byproducts of other evolved cognitive capabilities. (Some evolutionary psychologists have claimed that traits like art and music were the direct objects of selection, since proficiency in those arts conferred on those higher reproductive success.)
Kevin Laland discusses the recent evidence in the genome for selection on humans; this involves population-genetic analysis of “selective sweeps,” which can detect signatures of natural selection by looking at the diversity of DNA variation around various genes. Low diversity in a region indicates that a nearby gene has recently undergone a “fixation,” that is, a single “allele,” or gene copy, has risen to high frequency from one or a few original mutations. See my previous post on this work.
Spencer Wells talks about genetic changes due to migration, concentrating on genes affecting skin pigmentation. He fails to mention, though, that that this story is still not well understood, and that there’s controversy about the classic “melanoma versus vitamin D” explanation.
Finally, Anna di Rienzo discusses her lab’s work on the Duffy antigen showing recent selection for malaria resistance, and talks about work on other “disease genes.”
It’s a good short summary for the layperson. I love the eloquence of these scientists, as well as the timbre of Pinker’s voice and Steve Jones’s hybrid Welsh/English accent (his take on a Cro-Magnon man riding the bus in Camden Town is hilarious). My only plaint: there could have been a bit more discussion of evidence for evolution via cultural change, that is, the “gene-culture coevolution” as exemplfied by the evolution of lactose tolerance in pastoral human populations (I talk about this in WEIT, and have posted on it here.
The question about evolution I get most often when talking to the general public is this: “Are humans still evolving?” If you can’t answer that question, you’ll be able to after a half-hour investment in listening to the show.