The bones of long - dead species usually reveal little about their societal behavior , but a study of four ape specie suggests there might be an exclusion in the sagittal crest , the bony ridge some have at the top of the skull . These ridges provide space for brawniness to tie to , allowing stronger chewing , but new research indicates they also act as a form of male social signaling .
gorilla ' dieting involve a lot of chewing , so it helps to have very strong temporalis muscles , and these need somewhere to spellbind . Sagittal peak provide this , and for a retentive time this was mean to be the death of the story . However , Dr Katharine Baloliaof the Australian National University direct out that the crests are often larger than they need to be for muscle attachment alone . former research has shown that distaff gorillas find a big crown a spot of a turn on , and materialisation born to large - crested males are more successful .
Balolia also take down that some nonextant human relatives , particularly some members of the Australopithecus genus , had striking crests , although by the time our own genus had evolved crests were almost entirely go . She wondered if the crests could inform us , not just about the foods our ancestors ate , but how they interact .
In theJournal of AnatomyBalolia account on a comparison of the crests in four copycat specie . She shows that in western lowland gorillas and orang the timing of crest organisation coincides with males becoming dominant and competing for mates . In gorillas , this happens shortly after the wisdom tooth come forth , but male orangutans have a recollective period of sub - dominant adulthood . The crown only emerge when they are ready to claim territory , later in life .
Female Gorilla gorilla also grow a crown , but it is little and emerge more slowly , suggesting its purpose is for jaw , not show .
On the other bridge player , lar gibbons rarely train a crest at all . Balolia thinks this reflects lower levels of manly - male conflict , and therefore less motivation for glossy signs of dominance .
metal money have plenty of other frame of intimate signal , but most do n’t fossilize well . If , as Balolia suspects , the absence of a top among imitator indicates a capacity for multiple adult males to hold out together , its disappearance could help us sympathise the evolution of societal behavior in long - pop off ancestors .
“ If sagittal crest size and societal behavior are linked in this style , then we could potentially make that some of our out human relatives had a gorilla - corresponding societal scheme , ” Balolia say in astatement . " This would be a first because otherwise , the human fossil record provide cherished little about how our extinct relatives chose their mates . "
That ’s a very telling sagittal crest you ’ve got there . Bet the dame love it . Kari K / Shutterstock
