One study even suggests that we become adapted for endurance running ( nature , vol 432 , p 345 ) , although modern couch potatoes may consider this idea a step too far .
In a more compelling evolutionary explanation bipedalism would substantially boost survival , which is why some people believe it evolved to allow males to access more food so that they could help feed their partners and offspring ( odyssey , vol 2 , p 12 ) .
To examine how languages have diversified over the course of human history , my colleagues and I drew up family trees for three large language groups - indo-european languages , the bantu languages of africa , and polynesian languages from oceania ( science , vol 319 , p 588 ) .
Importantly , the ratio of large to small avalanches fit the predictions of the computational models that had first suggested that the brain might be in a state of self-organised criticality ( the journal of neuroscience , vol 23 , p 11167 ) .
One study in mice , for example , found that an alternate-day fast for six months reduced the heart 's ability to pump blood ( journal of cardiac failure , vol 16 , p 843 ) .
Beggs 's team noticed that certain chains of neurons would fire repeatedly in avalanches , sometimes over several hours ( the journal of neuroscience , vol 24 , p 5216 ) .
He thinks the latter forms of " forced " laughter probably evolved later , to fine-tune our manipulation of social situations ( quarterly review of biology , vol 80 , p 395 ) .
His explanation stems from the observation that during adolescence , girls and boys undergo their own characteristic patterns of growth and development ( american journal of human biology , vol 21 , p 567 ) .
The human genome contains more than 26 000 of these so-called indels many linked with differences in gene expression between humans and chimps ( mobile dna vol 2 p 13 ) .