Mouthing off

Published on 26/03/2004 00:00

HUMANS may have their puny jaws to thank for growing big brains.

American researchers have discovered a genetic defect that led our ape-like ancestors to develop weak jaw muscles 2.4 million years ago.

The mutation preceded the first appearance of modern human-like features in the fossil record, including a large braincase.

This led the scientists to conclude that it was the weakened jaw - effectively an inherited "disease" - that allowed human skulls and brains to grow.

Dr Nancy Minugh-Purvis, of the University of Pennsylvania in Philadelphia, said: "The coincidence in time of the gene-inactivating mutation and the advent of a larger braincase in some early Homo populations may mean that the decrease in jaw-muscle size and force eliminated stress on the skull, which "released" an evolutionary constraint on brain growth."

Defence rules

INVASIVE plants have been out-competed by existing vegetation, which has successfully defended its habitat.

An experiment by German scientists has found that offspring from invasive North American populations of garlic mustard (Alliaria petiolata) were out-competed by those from native European populations.

The researchers, from the Centre for Environmental Research in Halle, believe the species has evolved to be less, rather than more, competitive - probably due to a lack of strong competitors in the invaded habitats.

Long odds

AN international team of physicists believe they have found a subatomic "golden needle" in a micro-cosmic haystack.

The scientists have discovered evidence of a highly sought-after process from among 7.8 trillion possible sources while investigating an extremely rare form of subatomic particle decay.

The group, based at the US department of energy’s Brookhaven National Laboratory in New York state, said it could be an indication of new forces beyond those incorporated in the standard model of particle physics.

Under this long-standing model, the rate of such decays would be half that observed by the researchers, although it is still too early to say if a deviation has occurred. The innovative experiment used the most comprehensive particle detector ever built, located at the lab.

The experiment detected the disintegration of an unstable subatomic particle called a K meson, which can decay, or break apart, in a variety of ways.

One particular decay - in which the K meson turns into other particles - is very important due to the internal subatomic processes involved and its sensitivity to new physical effects not accounted for in the standard model.

• Sources: Nature, Ecology Letters, US Brookhaven National Laboratory