HENRY

A new paper from Manfred Kayser’s group - Patterns of Y-chromosome Diversity Intersect with the Trans-New Guinea Hypothesis:

The island of New Guinea received part of the first human expansion out of Africa (> 40.000 years ago), but its human genetic history remains poorly understood. In this study, we examined Y-chromosome diversity in 162 samples from the Bird’s Head region of northwest New Guinea, and compared the results with previously obtained data from other parts of the island.

Northwest New Guinea harbours a high level of cultural and linguistic diversity and is inhabited by non-Austronesian (i.e. Papuan) speaking groups as well as harbouring most of West New Guinea’s Austronesian-speaking groups. However, 97.5% of its Y-chromosomes belong to five haplogroups that originated in Melanesia; hence, the Y-chromosome diversity of northwest New Guinea (and, according to available data, of New Guinea as a whole) essentially reflects a local history. The remaining 2.5% belong to two haplogroups (O-M119 and O-M122) of East Asian origin, which were brought to New Guinea by Austronesian-speaking migrants around 3,500 years ago.

Thus, the Austronesian expansion had only a small impact on shaping Y-chromosome diversity in northwest New Guinea, although the linguistic impact of this expansion to this region was much higher. In contrast, the expansion of Trans-New Guinea speakers (non-Austronesian) starting about 6,000-10,000 years ago from the central highlands of what is now Papua New Guinea, presumably in combination with the expansion of agriculture, played a more important role in determining the Y-chromosome diversity of New Guinea. In particular, we identified two haplogroups (M-P34 and K-M254) as suggestive markers for the Trans-New Guinea expansion, whereas two other haplogroups (C-M38 and K-M9) most likely reflect the earlier local Y-chromosome diversity. We propose that sex-biased differences in the social structure and cultural heritage of the people involved in the Austronesian and the Trans-New Guinea expansions played an important role (among other factors) in shaping the New Guinean Y-chromosome landscape.

Jonathan Haidt at talks about moral psychology and the misunderstanding of religion at Edge:

In what follows I will take it for granted that religion is a part of the natural world that is appropriately studied by the the methods of science. Whether or not God exists (…), religiosity is an enormously important fact about our species.There must be some combination of evolutionary, developmental, neuropsychological, and anthropological theories that can explain why human religious practices take the various forms that they do, many of which are so similar across cultures and eras.

It’s an excellent article that takes a cutting edge approach to the psychology of religion. Go check it out.

This week’s Science is a special issue on social cognition, and has a bundle of fun little articles (all of which are subscription only), starting with a review of “Social Components of Fitness in Primate Groups” by Joan Silk:

There is much interest in the evolutionary forces that favored the evolution of large brains in the primate order. The social brain hypothesis posits that selection has favored larger brains and more complex cognitive capacities as a means to cope with the challenges of social life. The hypothesis is supported by evidence that shows that group size is linked to various measures of brain size. But it has not been clear how cognitive complexity confers fitness advantages on individuals. Research in the field and laboratory shows that sophisticated social cognition underlies social behavior in primate groups. Moreover, a growing body of evidence suggests that the quality of social relationships has measurable fitness consequences for individuals.

This is followed by Herrmann et al’s “Humans Have Evolved Specialized Skills of Social Cognition: The Cultural Intelligence Hypothesis“, where they test the idea that one of the reasons that humans are smart is because we’ve developed a special set of cognitive skills for handling social tasks:

Humans have many cognitive skills not possessed by their nearest primate relatives. The cultural intelligence hypothesis argues that this is mainly due to a species-specific set of social-cognitive skills, emerging early in ontogeny, for participating and exchanging knowledge in cultural groups. We tested this hypothesis by giving a comprehensive battery of cognitive tests to large numbers of two of humans’ closest primate relatives, chimpanzees and orangutans, as well as to 2.5-year-old human children before literacy and schooling. Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more “general intelligence,” we found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that the children had more sophisticated cognitive skills than either of the ape species for dealing with the social world.

Next up is another paper by Robin Dunbar and Susanne Shultz on Evolution in the Social Brain (henry covered their previous paper too):

The evolution of unusually large brains in some groups of animals, notably primates, has long been a puzzle. Although early explanations tended to emphasize the brain’s role in sensory or technical competence (foraging skills, innovations, and way-finding), the balance of evidence now clearly favors the suggestion that it was the computational demands of living in large, complex societies that selected for large brains. However, recent analyses suggest that it may have been the particular demands of the more intense forms of pairbonding that was the critical factor that triggered this evolutionary development. This may explain why primate sociality seems to be so different from that found in most other birds and mammals: Primate sociality is based on bonded relationships of a kind that are found only in pairbonds in other taxa.

Heading right down the cognitive path is Prospection: Experiencing the Future by Gilbert and Wilson, who review some recent work on “mental time travel”:

All animals can predict the hedonic consequences of events they’ve experienced before. But humans can predict the hedonic consequences of events they’ve never experienced by simulating those events in their minds. Scientists are beginning to understand how the brain simulates future events, how it uses those simulations to predict an event’s hedonic consequences, and why these predictions so often go awry.

Seen on reddit, Richard Feynman “explodes in horror” when asked to review textbooks:

…the next day I got a telephone call from a pretty famous lawyer here in Pasadena, Mr. Norris, who was at that time on the State Board of Education. He asked me if I would serve on the State Curriculum Commission, which had to choose the new schoolbooks for the state of California. You see, the state had a law that all of the schoolbooks used by all of the kids in all of the public schools have to be chosen by the State Board of Education, so they have a committee to look over the books and to give them advice on which books to take.

…Finally I come to a book that says, “Mathematics is used in science in many ways. We will give you an example from astronomy, which is the science of stars.” I turn the page, and it says, “Red stars have a temperature of four thousand degrees, yellow stars have a temperature of five thousand degrees . . .” — so far, so good. It continues: “Green stars have a temperature of seven thousand degrees, blue stars have a temperature of ten thousand degrees, and violet stars have a temperature of . . . (some big number).” There are no green or violet stars, but the figures for the others are roughly correct. It’s vaguely right — but already, trouble! That’s the way everything was: Everything was written by somebody who didn’t know what the hell he was talking about, so it was a little bit wrong, always! And how we are going to teach well by using books written by people who don’t quite understand what they’re talking about, I cannot understand. I don’t know why, but the books are lousy; UNIVERSALLY LOUSY!

Anyway, I’m happy with this book, because it’s the first example of applying arithmetic to science. I’m a bit unhappy when I read about the stars’ temperatures, but I’m not very unhappy because it’s more or less right — it’s just an example of error. Then comes the list of problems. It says, “John and his father go out to look at the stars. John sees two blue stars and a red star. His father sees a green star, a violet star, and two yellow stars. What is the total temperature of the stars seen by John and his father?” — and I would explode in horror.

Continued in “Judging Books by Their Covers“

For centuries, anthropologists have travelled overseas to live among ‘strange’ tribes and observe their ‘colourful’ ways. But rarely has it been tried the other way round. So what happened when a group of South Pacific islanders spent a month in Britain to study our own odd little lives?

Oh dear… lots of talk of firewater and quaint little natives in this one…

The British Psychological Society blog is reporting on research showing that autistic children are “immune” to contagious yawning:

Footage of the children taken while they were watching the videos showed, as expected, that the non-autistic children yawned more during and after seeing a video of a person yawning, than after watching a control video. By contrast, the children with autism yawned no more after seeing a yawn video than after a control video – they appeared to be immune to the contagious effects of yawning. This remained true even after the researchers controlled for the effects of age and intelligence.

Scholz et al in East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins (Open Access):

The environmental backdrop to the evolution and spread of early Homo sapiens in East Africa is known mainly from isolated outcrops and distant marine sediment cores. Here we present results from new scientific drill cores from Lake Malawi, the first long and continuous, high-fidelity records of tropical climate change from the continent itself. Our record shows periods of severe aridity between 135 and 75 thousand years (kyr) ago, when the lake’s water volume was reduced by at least 95%.

Surprisingly, these intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum (LGM), the period previously recognized as one of the most arid of the Quaternary. From these cores and from records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa), we document a major rise in water levels and a shift to more humid conditions over much of tropical Africa after {approx} 70 kyr ago.

This transition to wetter, more stable conditions coincides with diminished orbital eccentricity, and a reduction in precession-dominated climatic extremes. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but our records provide evidence for dramatically wetter conditions after 70 kyr ago. Such climate change may have stimulated the expansion and migrations of early modern human populations.