Third cousin couples have the most children and grandchildren

Marriage between closely related cousins is a heavy taboo in many cultures and its critics often cite the higher risk of genetic diseases associated with inbreeding. That risk is certainly apparent for very close relatives, but a new study from Iceland shows that very distant relatives don’t have it easy either. In the long run, they have just as few children and grandchildren as closely related ones.

Shuffling the genetic deck

Sex chromosomes aside, every person has two copies of each gene, one inherited from their father and one by their mother. Not every gene will be in correct working order, but there’s a good chance that a faulty copy will be offset by a functional one from the other parent.

However, if two parents are closely related, there’s a higher-than-average chance that they will already share some of the same genes and a similarly increased chance that their child will receive two defective copies. That can be very bad news indeed and in cases where important genes are affected, the results can include miscarriage, birth defects or early death.

Sex, then, is a shuffling of their genetic deck and theoretically the more closely related the partners are, the greater the chance that their child will be dealt a dud hand. And yet, some studies have found that some closely related couples actually do better than distant relatives in terms of the number of children they manage to raise. This trend is certainly unexpected and the big question is whether it is the result of biology or money.

Ed vs. Gravity

For the next week, you’ll hear tumbleweeds blowing through this blog as I will be on holiday. I’m going to Whistler, Vancouver, where I will be sticking two flimsy strips of wood to my feet and throwing myself down a mountain at high speed. I see it as a challenge to both cold and gravity.

I’ll be writing a few things while I’m there so expect some good stuff the week after. For the moment, feel free to scour the Site Index for oldies-but-goodies or have a look at my Review of 2007 for more focused recommendations.

A word about comments: This blog’s comments policy are set so that anyone who’s had a comment previously approved can post more, but any newbies have to be moderated first. If you’ve never commented here before and your comment doesn’t show up until next week, that’s why.

New languages evolve in rapid bursts

The birth of new languages is accompanied by a burst of rapid evolution consisting of large changes in vocabulary that are followed by long periods of relatively slower change.

Languages are often compared to living species because of the way in which they diverge into new tongues over time in an ever-growing linguistic tree. Some critics have claimed that this comparison is a superficial one, a nice metaphor but nothing more.

But the new study by Quentin Atkinson, now at the University of Oxford, suggests that languages evolve at a similar stop-and-start pace, which uncannily echoes a long-standing theory in biology, known as ‘punctuated equilibrium’. The theory’s followers claim that life on Earth also evolved at an uneven pace, full of rapid bursts and slow periods.

Famously championed by the late Stephen Jay Gould, the punctuated equilibrium theory suggests that most species change very little over time and big evolutionary changes are concentrated at rare moments where new species branch off from existing lineages. Together with colleagues from the US and New Zealand, Atkinson found similar patterns in three of the worlds’ largest families of languages.

Malawi cichlids – how aggressive males create diversity

Certain groups of animals show a remarkable capacity for quickly evolving into new species to seize control of unexploited niches in the environment. And among these ecological opportunists, there are few better examples than the cichlids, a group of freshwater fishes that are one of the most varied group of back-boned animals on the planet.

In the words of Edward O. Wilson, the entire lineage seems “poised to expand.” The Great Lakes of Africa – Tanganyika, Malawi and Victoria – swarm with a multitude of different species; Lake Malawi alone houses over 500 that live nowhere else in the world.

All of these forms arose from a common ancestor in a remarkably short span of time. Now, a new study suggests that this explosive burst of diversity has been partly fuelled by rivalry between hostile males.

Michael Pauers of the Medical College of Wisconsin found that male cichlids have no time for other males that look like them and will bite, butt and threaten those who bear the same colour scheme. In doing so, they encourage diversity in the lake since mutant males with different tints are less likely to be set upon by territorial defenders.

Colour-changing chameleons evolved to stand out, not blend in

Chameleons aren’t exactly known for being showy. Indeed, they are so synonymous with blending in that we use the term ‘social chameleon’ to refer to people who are at home in any social setting. But new research suggests that this reputation needs a rethink. The chameleon’s ability to change colour evolved not to blend in, but to stand out.

Chameleons are a group of small lizards that are almost synonymous with camouflage. Common folklore has it that their vaunted ability to change their skin colour allows them to go undetected in a variety of environments.

Certainly, their default colours match their surroundings well. But Devi Stuart-Fox and Adnan Moussalli from South Africa have found that the changing hues they are best known for evolved for communication not disguise. They allow chameleons to make themselves incredibly but temporarily noticeable to mates and rivals, while remaining inconspicuous for the rest of the time.

Averaging photos creates infallible face recognition tool

Compare a photo of yourself all cleaned up for a night out with another one first thing the next morning, and you’ll begin to appreciate the problems that people working on face recognition software encounter.

While some unfeasibly lucky people look great from all angles, most of us have to contend with a lottery of lighting conditions, odd angles, stupid expressions, stupider poses and the ravages of age. Faced with this unavoidable variability, it’s no wonder that automatic software flounder when tasked with comparing images to stock photos, like those in passports.

Now, Rob Jenkins and Mike Burton from the University of Glasgow have beaten the problem by creating a face recognition system that, so far, has proved to be 100% accurate. This level of accuracy is unheard of in the technological world. It is matched only by that most sophisticated of computers – the human brain – and indeed, it’s the brain that provided Jenkins and Burton with the inspiration for their method.

Blind cavefish not so blind, Beetlemania and other tidbits…

Stories about cavefish are like buses – you get a seeming infinity of nothing and then loads turn up at once. Just 10 posts ago, I wrote about a study which found that you can restore sight to blind cavefish by cross-breeding individuals from different caves.

The different populations lost their eyes through changes to different sets of genes and in the hybrids, each faulty version was paired with a working one. As a result, the hybrids had fully formed and functional eyes despite having lived in darkness for a million years.

Now, a new study shows that the larvae of blind cavefish can detect light (or more accurately, shadows) too, even without working eyes. They can detect shadows and seek shelter in them, just like the sighted surface-dwelling versions of the same species. The key to the behaviour is their pineal gland, a small organ that regulates the body clock and, in some species, is sensitive to light.

I wrote up the research for Nature News; mosey on over for the full story and some possible explanations for why the fish’s pineal has retained the ability to detect light, even though its eyes have been lost.

Some other things to mention:

• The new edition of the Tangled Bank carnival is up at the Inoculated Mind.
• Nature picked up my David Attenborough interview for its Books and Arts section. My old lab colleagues from my PhD days would bust a gut laughing if they knew that I’d finally got my name into Nature…
• Nature Network’s published an interview I did with Alfried Vogler, who studies beetles at Imperial College. Last year, Vogler carried out the most comprehensive ever study on the evolutionary relationships between the beetles, the most successful group of animals on the planet.