One can speculate all day long about what a pre-neolithic diet consisted of...but as the paper points out:
Importantly, 11,000 years represent approximately 366 human generations, which comprise only 0.5% of the history of the genus Homo (Table 1).
The study was by Jared Roach and colleagues, and as you might guess from my post title, the result was surprising. Previous work had suggested a human mutation rate around 2.5 x 10-8 per site per generation. The new study found less than half the expected number of mutations between these parents and offspring, an estimated rate of only 1.1 x 10-8 per site.Yesterday Hawks blogged about another paper that seems to back up a slower than previously thought genetic mutation rate:
A new paper in Nature by Zhe-Xi Luo and colleagues reports the discovery of a 160-million-year-old early mammal, Juramaia, which they attribute to the placental mammal lineage. The news aspect is that this extends the chronology of fossil placental and marsupial mammals (the sister clade of placentals) by some 40 million years. That's a big chunk of time, but it's a really nice fossil which seems pretty clear in its morphology.On the other hand, maybe it just takes a few simple mutations to adapt to neolithic foods (prepared in a traditional manner, of course). It only took one mutation to turn off lactose intolerance, and that mutation has occurred in several populations engaging in animal husbandry independently. But that mutation is to simply continue the production of lactase. Humans, like all mammals, are already ridiculously well-adapted to milk--at least their own species' milk, not processed, when in infancy--beyond that, things can get dicey. How many mutations and selection are necesary to adjust to a diet heavy in grains, legumes and other neolithic cultivars?
I'm reading this closely because of the effect on the interpretation of mutation rates and the molecular clock. Obviously, if the earliest evidence for placental mammals used to be 120 million years ago, and now it's 160, that should affect the way we approach the genetic divergence of mammal lineages. In particular, when it comes to primates, some modern lineages are represented by fossils relatively early in the Cenozoic, suggesting that the common ancestor of all the primates may have been much earlier, deep in the Cretaceous period.
How well adapted we are to neolithic foods, which the paper cites as:
[...]cereal grains as staple foods, the introduction of nonhuman milk, domesticated meats, legumes and other cultivated plant foods, and later widespread use of sucrose and alcoholic beverages. [ed. I see sucrose as more of a modern/industrial era food]Who knows, but one is probably better off avoiding them all as much as possible. I'm going to stick with this paradigm for now, I don't see the food reward/palatability hypothesis (FRH), especially as evoked by people with a strong bias towards "traditional" foods, as even coming close to supplanting it, or even supplementing it, at this point. Am I specifically going after Stephan Guyenet? Yes, I am. His blog is hugely influential and his recent "takedown" of the carbohydrate hypothesis and endorsement of FRH has been embraced by many influential bloggers. Maybe I'm just being reactionary, and I'm sure I'm guilty of my own confirmation bias, but I'm just not buying it.
