http://youtu.be/PfsJ5pyScPs

sujet du BAC à Pondichéry : http://fr.scribd.com/doc/136203156/SVT-S-obli

• 18 April 2013
• Magazine issue 2913. Subscribe and save
• For similar stories, visit the Editorials and Human Evolution Topic Guides

WHEN 9-year-old Matthew Berger stumbled upon an odd-looking bone in 2008, he could not have anticipated the import of his discovery. But his father Lee, a palaeontologist, had an inkling.

The shoulder and jawbone embedded in the rock turned out to come from a 2-million-year-old member of the human family, with anatomical features that suggest it is one of our early ancestors. Since then, more remains of Australopithecus sediba have been discovered, and the latest work on them is enriching our understanding of human evolution (see "Signs of human skin found on ancient ape ancestor").

We have unearthed more and more ancient human species in recent years. Rather than there being a neat evolutionary line from ape-like ancestor to modern human, we now think there was a lot of interbreeding. A. sediba is just one such ancestor; others may await discovery.

The focus of fieldwork is also shifting. The most famous discoveries come from East Africa, but A. sediba was found in the Malapa cave, north-west of Johannesburg. So southern Africa may be the place to seek insights into our origins. It will take sharp young eyes to spot them.

http://www.newscientist.com/article/mg21829132.900-heading-south-for-the-new-origin-of-our-species.html

http://www.newscientist.com/article/mg21829132.800-what-happens-when-hearts-become-spare-parts.html

• 18 April 2013
• Magazine issue 2913. Subscribe and save
• For similar stories, visit the Editorials Topic Guide

Lab-grown organs could be a boon for those on transplant waiting lists – but they also raise ethical questions

THE first heart transplant, back in 1967, was as shocking to some people as it was wondrous to others. The use of parts from one person to heal another – especially culturally resonant parts from dead donors – was a viscerally unsettling prospect.

Today, most of us consider a transplant to be a boon, albeit one that can only be granted to a limited number of people. Despite concerted efforts to increase the supply of donor organs, waiting lists are still lengthy in many places. What a further boon it would be, then, if we could make as many organs as we needed.

In this respect, the successful implantation of a lab-grown kidney in a rat this week is good news. Researchers are working hard to make the same techniques work with other organs – and in humans (see "Lab-grown kidney blazes trail for bespoke donor organs").

Even if all goes smoothly, it will be a long time before we take the first step: renewing donated organs that would otherwise go to waste because they are unsuitable for would-be recipients or in poor condition. These organs could be made viable by stripping them of donor cells, then recoating them with a patient's own.

This will not in itself solve the organ shortage. In the US, for example, around 18 per cent of donated kidneys go unused. Adding these to the 18,000 transplants conducted each year won't eliminate the 100,000-strong waiting list, although it will save many lives.

There is an alternative, albeit more distant. We could harvest organs from animals (most likely pigs) which can be stripped and then "humanised". If it works, this could let us meet the demand for organs in its entirety.

Would patients, and society, accept this? Almost 20 years ago, a front cover of asked: "Will a pig's heart end up in you?" That question remains open, as direct transplantation of major organs across species boundaries still hasn't been made to work.

But millions of people today do have body parts derived from pigs, such as heart valves and hernia patches. Pragmatism has won out over squeamishness, and acceptance will probably keep growing. The time may well come when the transplant of an animal's heart, too, seems more wondrous than shocking.

http://www.pourlascience.fr/ewb_pages/a/actualite-l-amour-est-dans-le-poil-31304.php

Messieurs, faut-il vous laisser pousser la barbe pour être plus séduisant ? Une étude américaine suggère que les femmes trouvent plus attirant un homme avec une bonne barbe de trois jours, mais pas une petite barbe de trois jours - plutôt un début de toison plus proche d’une semaine -, pensez à Ben Affleck dans Argo, récemment couronné aux Oscars.

Certains pourront pousser l’expérience jusqu’à la vraie barbe, selon leurs objectifs : lorsqu’il s’agit d’un flirt, les femmes sont plus attirées par une barbe de trois jours, et pour une relation durable avec enfants à la clé, elles semblent favoriser une barbe de Mathusalem. Les barbus, apparemment, sont considérés comme de bons candidats à la paternité, et les femmes y sont plus sensibles, d’après l’étude, lorsqu’elles sont en période de fertilité maximale, au milieu de leur cycle. A chacun sa barbe, à chacun ses amours.

http://www.ehbonline.org/article/S1090-5138%2813%2900022-6/abstract

The role of facial hair in women's perceptions of men's attractiveness, health, masculinity and parenting abilities

Facial hair strongly influences people's judgments of men's socio-sexual attributes. However, the nature of these judgments is often contradictory. The levels of intermediate facial hair growth presented to raters and the stage of female raters' menstrual cycles might have influenced past findings. We quantified men's and women's judgments of attractiveness, health, masculinity and parenting abilities for photographs of men who were clean-shaven, lightly or heavily stubbled and fully bearded. We also tested the effect of the menstrual cycle and hormonal contraceptive use on women's ratings. Women judged faces with heavy stubble as most attractive and heavy beards, light stubble and clean-shaven faces as similarly less attractive. In contrast, men rated full beards and heavy stubble as most attractive, followed closely by clean-shaven and light stubble as least attractive. Men and women rated full beards highest for parenting ability and healthiness. Masculinity ratings increased linearly as facial hair increased, and this effect was more pronounced in women in the fertile phase of the menstrual cycle, although attractiveness ratings did not differ according to fertility. Our findings confirm that beardedness affects judgments of male socio-sexual attributes and suggest that an intermediate level of beardedness is most attractive while full-bearded men may be perceived as better fathers who could protect and invest in offspring.