Did Neanderthal cells cook as the climate warmed?

by Ewen Callaway

This Neanderthal skeleton was found in 1856 in the Neander Valley in Mettmann (Image: Action Press / Rex Features)

Neanderthals may have gone extinct because their cells couldn't cope with climate change, according to a new hypothesis presented at a genetics conference this month.

Metabolic adaptations to Ice Age Europe may have proved costly to Neanderthals after the continent's climate started to change, says Patrick Chinnery, a molecular biologist at Newcastle University, UK.

He and colleague Gavin Hudson identified potentially harmful mutations in the newly sequenced Neanderthal mitochondrial genome. In particular, the researchers found genes that are associated with neurodegenerative diseases and deafness. "If they were found in modern humans they would be bad news," Chinnery says.

The extinction of Neanderthals, close relatives of modern humans, some 25,000 years ago remains unexplained.

One theory holds that they were physically outcompeted by modern humans , another that they were economically eclipsed by us.. Yet another theory suggests that Neanderthals couldn't adapt to climate change.

Cooked cells?

The discovery of harmful mutations in the Neanderthal mitochondrial genome supports the climate-change idea, with a twist.

Chinnery and Hudson suggest that mutations in mitochondria helped Neanderthals cope with the cold weather, but that when the climate started fluctuating between warm and cold periods, they were at a disadvantage.

In all cells, from yeast to human, a mitochondrion's main job is to produce the energy that powers cells - this takes the form of a chemical called ATP. Our mitochondria do this quite efficiently under ideal conditions, making 36 ATP molecules with the energy stored in a single molecule of glucose sugar.

Mutations that sap this efficiency would generate heat instead - a potentially useful trick for Neanderthals who are known to have had adaptations to cold weather, Chinnery says. However, a warmer and less climatically stable habitat could have spelled trouble for Neanderthals with such mutations.

Perhaps the Neanderthals' mitochondrial DNA adapted them to the cold, and they couldn't cope when the climate started to change, he says.

Mum's mitochondria

However, with only a single Neanderthal DNA sequence decoded so far, that hypothesis remains provisional.

"This 'n of 1' experiment raises a question which needs to be tested on a large number of cases," Chinnery says.

They might not have to wait long. "We hope to be able to provide [Neanderthal] subjects for doing that kind of analysis really soon," says Edward Green, a researcher at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Green and colleague Svante Pääbo published the first complete Neanderthal mitochondrial genome earlier this year.

However, Green cautions against reading too much into a Neanderthal's - or a human's - mitochondria.

Unlike DNA in the cell's nucleus, mitochondrial DNA does not reflect a healthy mix of maternal and paternal genes. We inherit all mitochondrial genes from our mothers, so a potentially advantageous gene has no way to spread through a population, without bringing along the rest of the genome.

Most scientists contend that changes to mitochondrial genes instead occur by chance, making them a good marker for human and Neanderthal ancestry.

Original here

Patternicity: Finding Meaningful Patterns in Meaningless Noise

By Michael Shermer

Why do people see faces in nature, interpret window stains as human figures, hear voices in random sounds generated by electronic devices or find conspiracies in the daily news? A proximate cause is the priming effect, in which our brain and senses are prepared to interpret stimuli according to an expected model. UFOlogists see a face on Mars. Religionists see the Virgin Mary on the side of a building. Paranormalists hear dead people speaking to them through a radio receiver. Conspiracy theorists think 9/11 was an inside job by the Bush administration. Is there a deeper ultimate cause for why people believe such weird things? There is. I call it “patternicity,” or the tendency to find meaningful patterns in meaningless noise.

Traditionally, scientists have treated patternicity as an error in cognition. A type I error, or a false positive, is believing something is real when it is not (finding a nonexistent pattern). A type II error, or a false negative, is not believing something is real when it is (not recognizing a real pattern—call it “apat­ternicity”). In my 2000 book How We Believe (Times Books), I argue that our brains are belief engines: evolved pattern-recognition machines that connect the dots and create meaning out of the patterns that we think we see in nature. Sometimes A really is connected to B; sometimes it is not. When it is, we have learned something valuable about the environment from which we can make predictions that aid in survival and reproduction. We are the ancestors of those most successful at finding patterns. This process is called association learning, and it is fundamental to all animal behavior, from the humble worm C. elegans to H. sapiens.

Unfortunately, we did not evolve a Baloney Detection Network in the brain to distinguish between true and false patterns. We have no error-detection governor to modulate the pattern-recognition engine. (Thus the need for science with its self-correcting mechanisms of replication and peer review.) But such erroneous cognition is not likely to remove us from the gene pool and would therefore not have been selected against by evolution.

In a September paper in the Proceedings of the Royal Society B, “The Evolution of Superstitious and Superstition-like Behaviour,” Harvard University biologist Kevin R. Foster and University of Helsinki biologist Hanna Kokko test my theory through evolutionary modeling and demonstrate that whenever the cost of believing a false pattern is real is less than the cost of not believing a real pattern, natural selection will favor patternicity. They begin with the formula pb > c, where a belief may be held when the cost (c) of doing so is less than the probability (p) of the benefit (b). For example, believing that the rustle in the grass is a dangerous predator when it is only the wind does not cost much, but believing that a dangerous predator is the wind may cost an animal its life.

The problem is that we are very poor at estimating such probabilities, so the cost of believing that the rustle in the grass is a dangerous predator when it is just the wind is relatively low compared with the opposite. Thus, there would have been a beneficial selection for believing that most patterns are real.

Through a series of complex formulas that include additional stimuli (wind in the trees) and prior events (past experience with predators and wind), the authors conclude that “the inability of individuals—human or otherwise—to assign causal probabilities to all sets of events that occur around them will often force them to lump causal associations with non-causal ones. From here, the evolutionary rationale for superstition is clear: natural selection will favour strategies that make many incorrect causal associations in order to establish those that are essential for survival and reproduction.”

In support of a genetic selection model, Foster and Kokko note that “predators only avoid nonpoisonous snakes that mimic a poisonous species in areas where the poisonous species is common” and that even such simple organisms as “Escherichia coli cells will swim towards physiologically inert methylated aspartate presumably owing to an adaptation to favour true aspartate.”

Such patternicities, then, mean that people believe weird things because of our evolved need to believe nonweird things.

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Written by Ophelia Deroy

(editor's note) Why are we interested in famous people? Evolutionary psychologists have suggested that social information served as gossip is inherently interesting for us - information about alliances, personal hatreds, couple formation and splits, is intrinsically rewarding to our brain - wherever it comes from, irrelevant though it might be to our own lives. Here, philosopher Ophelia Deroy sketches a different point of view.

"Fame" by David Bowie and John Lennon (1975) .

Perhaps it’s the imaginativeness of tabloids titles which surprises me every morning – anyway, stardom system remains very puzzling to me. I assume it serves a function – and even if it is obviously orchestrated by the medias and business companies (sponsorship for sport celebrities, brand names for singers, etc.), there must be something it appeals to in people...

What is the point of celebrity ?

But is it so sure ? Nick Couldry (LSE) complains about a lack of empirical evidence that celebrities really serve a function. The standard positions in debates about stardom and celebrity culture assume, at root, that the (quasi-industrial) production of celebrity discourse must contribute to some wider social function, whether we call it identity-formation or social integration or both. Here, for example, is McKenzie Wark: ‘we may not like the same celebrities, we may not like any of them at all, but it is the existence of a population of celebrities, about whom to disagree, that makes it possible to constitute a sense of belonging’ (M. Wark (1999) Celebrities, Culture and Cyberspace. Sydney: Pluto, p. 33,).

But, as Couldry asks, “where is the evidence that people ‘identify’ with celebrities in any simple way, or even that they regard ‘celebrity culture’ as important, rather than a temporary distraction, let alone that celebrities ‘make possible’ everyone’s sense of belonging?”. I guess the question is biaised (nobody claims that people “identify with celebrities in a simple way” ) but still, it addresses a legitimate worry : interest in celebrities life goes far beyond people for whom reference to these celebrities play a role in identity-formation or in conversation. Who has never read Hello Magazine over one’s shoulder in the tube? How come we all know about Madonna’s divorce – even when not caring for it? It is less obvious to me what function collecting these information serve for people whose sense of identity or belonging doesn’t apparently mix with celebrity gossips ? Is pure distraction a fair motive here?

The “it can happen to you too” effect .

Well, perhaps the question has to be addressed at a more general level. In a recent paper, Toby Young (the son of the sociologist Michaël Young, author of “The Rise of the Meritocracy”) compares attitudes to celebrities and to lottery :

Some commentators believe that the preponderance of reality shows and their casts of freaks and wannabes—the lumpen celebritariat—have devalued the whole notion of stardom. Yet the YouGov survey discovered that appearing on a reality television programme was a popular career option among teenagers, and another poll found 26 per cent of 16 to 19 year olds believe it is easy to secure a career in sports, entertainment or the media. If the existence of the celebrity class does play a role in securing people's consent to our winner-takes-all society, then the fact that the entry requirements are so low helps this process along. If people believe there is a genuine chance they might be catapulted to the top, they're more likely to endorse a system in which success is so highly rewarded. To paraphrase the advertising slogan for the National Lottery, it could be them. As with the lottery, people may know that the actual chances of winning are low but the selection mechanism itself is fair—a level playing field.

The paper concludes that the hidden function of celebrities would thus be to secure the consent of ordinary people to the unequal distribution of rewards, in a unfair absence of genuine equality of opportunity. Basically, you accept an unfair, qua arbitrary system if you think it’s nonetheless fair, qua almost random. Becoming famous is a question of luck – and you just wish you’ll be one of the lucky fews in the limo.

But then, if being famous is about being noticed and admired, you must known that you won’t be admired for any quality of yours – but just for being lucky, which anyone could have been.

Isn’t there here a resilient trace of the idea that people have « their own luck », and a kind of fate – that they bear responsibility for being lucky or not ?

At least this makes sense of two things.

The flux

First, why there should be a constant renewal of living celebrities – by contrast with a system with more perenial stars, or (dead, mythical) legendary figures : it shows that there is actually room for newcomers, and entertains every body’s dream to get his moment of fame.

Why celebrities are not heroes – but aren’t they still prestigious ?

Second, that there is room for typologies of celebrities. The ones that Young is talking about (by which he seems to mean some sort of pop stars) have nothing more special than their audience, except the fact that they managed to become famous – something which cannot be seen as a special achievement, on his perspective, but also has to be accessible to everyone. This contrasts with celebrities acknowledged for (a) their (moral, intrinsic) qualities or (b) their superior achievements, or (c) both. The later encourage a kind of deference, and their prestige rely on the fact that not everybody could have done what they did, or be where they are. So – questions –
How come that the first ones enjoy a kind of prestige, but without deference ? Is this a good typology of famous people ? Do you have another one ? Is there any constant among different cultures, and is the « random-star » just characteristic of (some) contemporary societies ?

The Limo problem

Still, Young’s analysis doesn’t distinguish between the desirability of being famous, and the desirability of having the material advantages that can go with fame (the limo), but not necessarily do. Also, it doesn’t seem that fame is desired as a mean – but as an end. You want to be in the Limo, not necessarily to have it. Or do you ?

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