A hunger to live longer

Want to live a long time? Who doesn’t? Quite a number of smart people have staked their hopes for long life on restricting their calorie intake. It’s an idea that rests on a not inconsiderable body of evidence. But some new developments suggest it may be a questionable strategy.

The idea that a diet containing a very modest energy content (measured in Calories or Kilojoules) could dramatically prolong lifespan is based on one of the most replicated findings in all of biology.

As long ago as 1935, researchers reported that lab rats fed dramatically restricted diets lived up to twice as long as rats allowed unrestricted access to food. The lifespan extending effects of dietary restriction appear to come about by delaying the onset of ageing and slowing the cellular damage and onset of diseases like cancers that naturally occur with age.

Since then, similar results have been obtained in mice, Rhesus monkeys, zebra fish, vinegar flies (Drosophila melanogaster), the nematode worm (Caenorhybditis elegans) and even yeast. The fact that dietary restriction prolonged lifespan and slowed ageing in such a variety of organisms strongly suggested that the underlying mechanisms are shared by all animals and possibly even all eukaryotes – the large group of complex organisms that includes animals, plants and fungi.

It didn’t take long for people to spot a potential route to slowing ageing and putting off the inevitable. Roy Walford championed what he called CRON – Calorie Restriction with Optimal Nutrition – in Beyond The 120-Year Diet. He argued that cutting dietary energy while maintaining micronutrient intake would prolong normal lifespan to well over a century, reducing the incidence of the major diseases of aging. Continue reading A hunger to live longer

The Origins of Racism

Could the prejudice against Collingwood supporters come from the same evolved tendencies that sometimes give rise to racism and religious bigotry? Source: woowoowoo on Flickr

A criticism often flung at evolutionary studies of human behaviour is that, in revealing the origins of the human psyche’s darkest aspects, they might substantiate our worst traits. The hysteria over sociobiology arose from concerns that a biological understanding of human behaviour and society would be used to justify racism, sexism and various other forms of prejudice.

Ideologues will usually grab at anything that suits their world-view and ignore whatever contradicts it. But that should not change the questions scientists ask. In fact modern evolutionary biology is making enormous contributions to our understanding of how our ideas of race, racism, gender and sexism arise.

In this vein, I have enjoyed catching up with some of the most recent research on the evolution and neurobiology of race and racism. Two of the most interesting reads are an article on the Roots of Racism by Elizabeth Culotta, and a Nature Neuroscience review by Jennifer Kubota and colleagues on the Neuroscience of Race.

Where does racism come from?

Culotta’s article, part of a special section in Science on Human Conflict, isolates two important themes that are gathering support. First, racism is one of many expressions of our evolved capacity to live and work in groups. The very human tendency to identify with an “us” defines the broader “them”.

Outgroup “hate”, then, is a mirror image of ingroup “love”. Religious bigotry, ethnic mistrust and even an intense dislike of Collingwood supporters arise at first from our tendency to form coalitions and allegiances.

The other important theme is that antipathy toward members of other groups gains much of its traction through fear, particularly of males. The snap judgments people make about others may be part of a sensitive alarm system that evolved when the people most likely to present a violent threat were strange males.

This idea is part of a simmering discussion about the importance of male aggression in human evolution. According to the “Male Warrior Hypothesis”, men have evolved stronger tendencies to form coalitions to attack other groups and to defend their own groups, families and property against coalitions of other men. Continue reading The Origins of Racism