Posts Tagged ‘evolution’

Paleofantasy

Friday, April 26th, 2013

Book review: Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live, by Marlene Zuk

This book refutes some myths about what would happen if we adopted the lifestyle of some imaginary hunter-gather ancestor who some imagine was perfectly adapted to his environment.

I’m a bit disappointed that it isn’t as provocative as the hype around it suggested. It mostly just points out that there’s no single environment that we’re adapted to, plus uncertainty about what our ancestors’ lifestyle was.

She spends a good deal of the book demonstrating what ought to be the well-known fact that we’re still evolving and have partly adapted to an agricultural lifestyle. A more surprising point is that we still have problems stemming from not yet having fully evolved to be land animals rather than fish (e.g. hiccups).

She provides a reference to a study disputing the widely held belief that the transition from hunter-gatherer to farmer made people less healthy.

She cites evidence that humans haven’t evolved much adaptation to specific diets, and do about equally well on a wide variety of diets involving wild foods, so that looking at plant to animal ratios in hunter-gather diets isn’t useful.

Her practical lifestyle advice is mostly consistent with an informed guess about how we can imitate our ancestors’ lifestyle (e.g. eat less processed food), and mainly serves to counteract some of the overconfident claims of the less thoughtful paleo lifestyle promoters.

The Beginning of Infinity

Friday, April 20th, 2012

Book review: The Beginning of Infinity by David Deutsch.

This is an ambitious book centered around the nature of explanation, why it has been an important part of science (misunderstood by many who think of science as merely prediction), and why it is important for the future of the universe.

He provides good insights on jump during the Enlightenment to thinking in universals (e.g. laws of nature that apply to a potentially infinite scope). But he overstates some of its implications. He seems confident that greater-than-human intelligences will view his concept of “universal explainers” as the category that identifies which beings have the rights of people. I find this about as convincing as attempts to find a specific time when a fetus acquires the rights of personhood. I can imagine AIs deciding that humans fail often enough at universalizing their thought to be less than a person, or that they will decide that monkeys are on a trajectory toward the same kind of universality.

He neglects to mention some interesting evidence of the spread of universal thinking – James Flynn’s explanation of the Flynn Effect documents that low IQ cultures don’t use the abstract thought that we sometimes take for granted, and describes IQ increases as an escape from concrete thinking.

Deutsch has a number of interesting complaints about people who attempt science but are confused about the philosophy of science, such as people who imagine that measuring heritability of a trait tells us something important without further inquiry – he notes that being enslaved was heritable in 1860, but that was useless for telling us how to change slavery.

He has interesting explanations for why anthropic arguments, the simulation argument, and the doomsday argument are weaker in a spatially infinite universe. But I was disappointed that he didn’t provide good references for his claim that the universe is infinite – a claim which I gather is controversial and hasn’t gotten as much attention as it deserves.

He sometimes gets carried away with his ambition and seems to forget his rule that explanations should be hard to vary in order to make it hard to fool ourselves.

He focuses on the beauty of flowers in an attempt to convince us that beauty is partially objective. But he doesn’t describe this objective beauty in a way that would make it hard to alter to fit whatever evidence he wants it to fit. I see an obvious alternative explanation for humans finding flowers beautiful – they indicate where fruit will be.

He argues that creativity evolved to help people find better ways of faithfully transmitting knowledge (understanding someone can require creative interpretation of the knowledge that they are imperfectly expressing). That might be true, but I can easily create other explanations that fit the evidence he’s trying to explain, such as that creativity enabled people to make better choices about when to seek a new home.

He imagines that he has a simple way to demonstrate that hunter-gatherer societies could not have lived in a golden age (the lack of growth of their knowledge):

Since static societies cannot exist without effectively extinguishing the growth of knowledge, they cannot allow their members much opportunity to pursue happiness.

But that requires implausible assumptions such as that happiness depends more on the pursuit of knowledge than availability of sex. And it’s not clear that hunter-gatherer societies were stable – they may have been just a few mistakes away from extinction, and accumulating knowledge faster than any previous species had. (I think Deutsch lives in a better society than hunter-gatherers, but it would take a complex argument to show that the average person today does).

But I generally enjoyed his arguments even when I thought they were wrong.

See also the review in the New York Times.

RNA in our food

Monday, October 10th, 2011

What you eat can influence your gene expression.

A post titled Eat Your Grains says:

RNA from our food can survive digestion, sneak into our cells, and control our genes

Researchers studied MicroRNAs from rice that affect cholesterol levels in mice. The effect appears harmful, which is a kind of defense against predation I’d expect from something that hasn’t evolved to cooperate with animals. (Grains have probably evolved some traits that help humans, but only where farmers have long been aware of the traits). Oddly, the researchers say “miRNAs may serve as a novel essential nutrient”, but I expect them to be harmful on average, except in fruits (which have evolved to attract animals).

The 10,000 Year Explosion

Sunday, March 15th, 2009

Book review: The 10,000 Year Explosion: How Civilization Accelerated Human Evolution by Gregory Cochran and Henry Harpending.

This provocative book describes many recent genetic changes in humans, primarily those resulting from the switch from hunter-gatherer lifestyles to agricultural lifestyles. Large changes in diets and disease are the simplest causes of change, but the book also describes subtler influences that alter human minds as well.

I had believed that large populations rarely evolve very fast due to the time required for a mutation to spread. This is true for mutations which provide negligible selective advantage, but the book shows that it’s plausible that a number of mutations have recently gained a large enough selective advantage that the rate at which they become widespread is only modestly dependent on population size. Also, the book makes a surprising but plausible claim that the larger supply of mutations in large populations can mean large populations evolve faster than small populations.

The book is occasionally not as rigorous as I would like. For instance, the claim that Ashkenazi “must have been exposed to very similar diseases” as their neighbors is false if the diseases were sexually transmitted.

Most of their claims convince me that conventional wisdom underestimates how important human genetic differences compared to cultural differences, but leave plenty of room for doubt about the magnitude of that underestimation.

They provide an interesting counterargument to the claim that differences within human populations are larger than the differences between populations. Their belief that differences between populations are more important seems to rest on little more than gut feelings, but they convince me that the conventional wisdom they’re disputing is poorly thought out.

They convinced me to take more seriously the possibility that some Neanderthal genes have had significant effects on human genes, although I still put the odds on that at less than 50 percent.