Neanderthals more like Modern Humans than we thought?

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There’s an inter­est­ing press release below the fold. Examination of Neanderthal teeth sug­gests that their child­hood phase was a lot longer than pre­vi­ously thought. It is cur­rently thought that Neanderthal chil­dren grew up a lot faster than their mod­ern coun­ter­parts. A big bit of the evid­ence in favour of this is exam­in­a­tion of perikymata. These are mark­ings in teeth that show how the tooth grew, a bit like rings in tree trunks.

Previous work sug­ges­ted that Neanderthals grew up to 15% faster than mod­ern humans. Thus they reached matur­ity faster and this meant less time was neces­sary for guid­ing them to matur­ity. This is a handy thing, as evid­ence of age of death sug­gests that a Neanderthal was doing well to reach thirty. In addi­tion they were mar­tyrs to arth­ritis, so it would be an advant­age to have rap­idly grow­ing children.

However Debra Guatelli-Steinberg, an anthro­po­logy pro­fessor, at Ohio State has gone back and examined what yard­stick was used to meas­ure the Neanderthal growth against. Teaming up with aca­dem­ics from other uni­ver­sit­ies she’s examined teeth from a wide vari­ety of mod­ern people and found that Neanderthal growth actu­ally falls within a com­par­able range.

This is poten­tially very excit­ing. If Neanderthal chil­dren did take a lot of care, where did this come from? Normally you’d expect the par­ents, but in this case there’s a strong pos­sib­il­ity that the par­ents would be injured or dead, and the longer the child­hood, the more likely a child is to become an orphan while a depend­ent. We’ve ten­ded to think that life for a Neanderthal was nasty, bru­tish and short – and that they were too. Instead more and more evid­ence is sug­gest­ing that they were rather sophisticated.

I’ve now dis­covered there’s a Dental Anthropology Association. That sounds like hard work.

The press release is below.

NEANDERTHAL TEETH GREW NO FASTER THAN COMPARABLE MODERN HUMANS
COLUMBUS , Ohio – Recent research sug­ges­ted that ancient Neanderthals might have had an accel­er­ated child­hood com­pared to that of mod­ern humans but that seems flawed, based on a new assess­ment by research­ers from Ohio State University and the University of Newcastle .

They found that the rate of tooth growth present in the Neanderthal fossils they examined was com­par­able to that of three dif­fer­ent pop­u­la­tions of mod­ern humans.

And since the rate of tooth growth has become a more-accepted tool for estim­at­ing the length of child­hood among hom­in­ids, the find­ing is the latest evid­ence sug­gest­ing that Neanderthals may not have been as dif­fer­ent from mod­ern humans as some research­ers have thought.

The study by Debbie Guatelli-Steinberg, assist­ant pro­fessor of anthro­po­logy at Ohio State , appeared in the cur­rent issue of the Proceedings of the National Academy of Sciences. Donald J. Reid, lec­turer in oral bio­logy at the University of Newcastle , Thomas A. Bishop, asso­ci­ate pro­fessor of stat­ist­ics, and Clark Larsen, pro­fessor and chair of anthro­po­logy, both at Ohio State , were co-authors in the study.

Based on our study of the enamel of these Neanderthal teeth and other mod­ern ones, we can’t sup­port the claim that Neanderthals grew up more quickly than do mod­ern humans,” she said.

Key to this con­clu­sion are micro­scopic lines on the out­side of teeth that mark the incre­mental growth of enamel on a young tooth. Like tree rings that can gauge the age of a red­wood, these stri­ations – called perikymata – record new growth on the sur­face of the tooth.

Researchers know from earlier work that these mark­ings are present in all form­ing teeth, sig­ni­fy­ing six to 12 days of growth. By mul­tiply­ing that inter­val by the num­ber of perikymata on a tooth’s sur­face, research­ers can gauge how long it took for the tooth to mature. And that gives them an indic­a­tion of the length of an individual’s childhood.

Neanderthals, Homo neander­thalen­sis, were the dom­in­ant hom­inid inhab­it­ing most of what is now Europe and west­ern Asia . Remains have been found as far south as Iraq and as far north as Great Britain . Fossil skulls reveal the dis­tinct­ively prom­in­ent brows and miss­ing chins that set them apart from later humans.

They thrived from about 150,000 to 30,000 years ago until their lin­eage failed for as-yet unknown reas­ons. Most research­ers have argued that their life in extremely harsh, Ice Age-like envir­on­ments, coupled with their lim­ited tech­no­lo­gical skills, ulti­mately led to their demise.

In a study pub­lished last year in the journal Nature, other research­ers con­ten­ded that Neanderthal teeth took 15 per­cent less time to reach matur­ity than those in later Homo sapi­ens, sug­gest­ing to them that a Neanderthal child­hood would be shorter than our own.

But Guatelli-Steinberg’s team wanted a broader com­par­ison and there­fore com­pared the teeth from Neanderthals to those of three mod­ern pop­u­la­tions – people cur­rently liv­ing in Newcastle-upon-Tyne , U.K. ; indi­gen­ous people from south­ern Africa, and Inuit from Alaska dat­ing from 500 B.C. until the present.

We chose these three groups since they would provide a good cross-section of vari­ous pop­u­la­tions from dif­fer­ent regions of the world,” she said. “We feel that they give us some insights into the vari­ation that exists within mod­ern humans.”

For the study, the research­ers used pre­cise dental impres­sions Guatelli-Steinberg and Larsen made of 55 teeth believed to come from 30 Neanderthal indi­vidu­als. These were com­pared to 65 teeth from 17 Inuit, 134 teeth from 114 south­ern Africans and 115 teeth from as many Newcastle res­id­ents. In all cases, the research­ers tal­lied the num­ber of perikymata on the enamel sur­face of the teeth.

Guatelli-Steinberg said that the res­ults showed that the enamel form­a­tion times for the Neanderthals fell eas­ily within the range of time shown by teeth from the three mod­ern pop­u­la­tions – a con­clu­sion that did not sup­port a shorter child­hood for the Neanderthals.

Enticing though it may be, these new find­ings haven’t con­vinced the research­ers that a Neanderthal child­hood was equal to a mod­ern human’s.

The miss­ing key bit of data to show that would be evid­ence for when the first molar tooth erup­ted in the Neanderthals, and we simple have no evid­ence of when that occurred,” she said.

The length of time is import­ant, the research­ers say, because unlike all other prim­ates, humans have an exten­ded period of child­hood growth, dur­ing which brain matures both in size and through exper­i­ences. Some earlier hom­in­ids matured far more quickly than mod­ern humans.

The ques­tion is when exactly did that pat­tern of devel­op­ment evolve in the growth of humans,” she said.

Support for this research came from a grant from the Leakey Foundation and from the College of Social and Behavioral Sciences at Ohio State.
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