Neanderthals, Brain Size, and Maturation

There is a new paper coming out in PNAS called Neanderthal brain size at birth provides insights into the evolution of human life history (wouldn’t you know it is not open access, so if anybody out there has access can you mail me a copy) that argues Neanderthals grew quickly but reached maturity later. The high growth rates placed greater demands on Neanderthal women and ultimately increased interbirth intervals. Consequently, they were out competed by anatomically modern Homo sapiens who had a shorter birth intervals, etc.

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Skull Fragments: A Frontal From Mongolia

It was published last month in C. R. Palevol 7 (2008) 51-60.

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Neanderthal Children And Flintknapping

Julien Riel-Salvatore over at A Very Remote Period Indeed has a thoughtful and thought provoking follow up to my recent post on Neanderthal children and flintknapping. Here is a small taste to tide you over till you get there:

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Finding Neanderthal Children In the Archaeological Record: Is There A Subconcious Bias?

PalArch’s Journal of Archaeology of Northwest Europe has an interesting article on toolmaking by Neanderthal children (see here for my previous post on the subject of children in the archaeological record). The article makes extensive use of research by Phillip Shelley, especially this article (if someone out there has access I would appreciate it if you could email me a copy).

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Neanderthal Teeth: How Did They Grow?

The above is a human tooth. If you look closely you can see faint grooves running horizontally across it’s surface. These grooves are called perikymata and represent growth. More specifically they represent growth cycles of about 6-14 days. Below is a high magnification detail from a thin section.


High magnification detail from the same thin section showing the regular growth structures found in enamel (polarised transmitted light microscopy). The approximately weekly growth layers, known as brown striae of Retzius, can be seen running from bottom left to top right. The enamel prisms run across from left to right, along which cross-striations can be seen (arrows). The cross-striations represent circadian (i.e. daily) growth markers and can be used to determine the precise timing of crown formation, as well as the timing of any disruption to this formation.

In theory one could count the number of perikymata on a tooth multiply it by 6-12 days and come up with an estimate of how long it took the tooth to form – getting at the same time an estimate of the length of childhood. Such studies have a long history in anthropology and recently this idea was applied to Neanderthal teeth. At issue is how long Neanderthals took to reach maturity – if they took less time than anatomically modern humans then that would obviously have bearing on the whole “Out of Africa/Multiregional Continuity” debate.
Recently a team of researchers performed a study on the perikymata of Neanderthal teeth:

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.

Neanderthals and Skeletal Biology

Back in April I wrote this post on skeltal biolgy. The post was about how several different techniques, such as stable isotope analysis, could reveal a lot about skeletal material. In that post I talked about how stable isotope anlysis helped document slavery in South Africa. Here is another, admittedly old, example.

There has been a certain amount of controversy in the anthropological literature concerning Neanderthal hunting ability. Although Neanderthals were freqently found in associatation with spear points, and other artifacts, and various faunal assemblages there has been some doubt about whether they were hunters or scavengers.

Neanderthal Skull Posted by Hello

In 2000 specimens from Vindija cave in Croatia were being radiocarbon dated. Part of the process includes the assessment of stable isotopes. To refresh your memory, stable isotopic analysis of carbon can be used to detect terrestrial versus marine diets. Stable isotopic analysis of nitrogen can be used to determine trophic level of the food consumed.

Neanderthal and Human Skeleton Posted by Hello
Thanks for the picture Dharma Bums

The analysis indicated that Neanderthals were acting as top-level carnivores and were securing animal protein mainly through hunting rather than scavenging.

The article I took this from is Neanderthal diet at Vindija and Neanderthal predation: The evidence from stable isotopes. You can also find more information here Stable isotope evidence for increasing dietary breadth in the European mid-Upper Paleolithic.
Additional interesting articles:

Constructive Interactions among Nutrients and Bone-Active Pharmacologic Agents with Principal Emphasis on Calcium, Phosphorus, Vitamin D and Protein

Animal Source Foods and Human Health during Evolution

Paleoecological reconstruction of a lower Pleistocene large mammal community using biogeochemical ({delta}13C, {delta}15N, {delta}18O, Sr:Zn) and ecomorphological approaches

Origins and evolution of the Western diet: health implications for the 21st century. I’ll have more to say about this article in a later post.

Cave Bears an Neanderthals

As mentioned several posts ago, scientists have succeeded in sequencing the nuclear DNA of cave bears. It is estimated that the DNA in question was approximately 40,000 years old. The possibility was raised the the technique could be used to sequence Neanderthal nuclear DNA. Previous attempts to sequence Neanderthal DNA focussed on mitochondrial DNA (a circular DNA found in the mitochondria of cells) with varying degrees of success. Interestingly enough, Neanderthals and Cave bears go together – more or less.

Drachenloch Cave Posted by Hello

At one time it was thought that Neanderthals had a cult centered around cave bears. Cave bear skeletons are found frequently in Europe. In several caves the bear skeletons were found, ostensibly, neatly arranged as if part of a shrine. The caves, such as Drachenloch above, contained largely intact bear skeletons neatly arranged around the periphery. At least one skelton was on a stone slab attributed to Neanderthal construction. Unfortunately for the theory, there are no Neanderthal artifacts, no cut markes indicative of human activity on the bones, no signs of Neanderthal occupation at all. Worse yet, the cave bear bones in the center areas of the cave were scrambled and broken while those at the periphery or in difficult to access areas were not. The cave bears occupied the cave for quite a while so skeletons in the center areas got trampled and disarticulated. Skeletons in the periphery were less likely to be disturbed. Further research indicates that carnivores – especially large ones – are actually quite rare at Neanderthal sites.

Sequencing Neanderthal DNA?

This is Way Cool

Two cave bears which died in Austria more than 40,000 years ago have had their nuclear DNA sequenced. The technique used to recover sequences from a tooth and a bone has more than doubled the record for the age of successfully recovered nuclear DNA – and Neanderthals could be next.

Recovering genetic material from ancient remains is fraught with difficulty because DNA degrades rapidly and is easily contaminated with external DNA, for example, by people handling the fossil. Most successful studies have focused on the more abundant mitochondrial DNA, but it is much less informative. In exceptional cases it has been possible to extract nuclear DNA from less than 20,000 years ago, preserved in permafrost or desert environments.

Follow the link for details.

Free Trade Caused the Neanderthals to go Extinct?

According to this article. According to the article, to be published in an upcoming issue of Journal of Economic Behavior and Organization, computer simulations indicate that neanderthals were done in by free trade. From the article:

“He cites archaeological evidence that suggests that humans, who joined Neanderthals in Europe about 40,000 years ago, specialised and traded both within and between regions. The evidence includes complex living quarters with different sections partitioned for different functions. Neanderthals, in contrast, lived in “largely unorganised” living spaces. (The Mousterian tool tradition was also fairly uniform acrioss a wide geographic area -afarensis)

There is also evidence that the early humans, mainly one population called the Gravettians, imported materials. Ivory, stones, fossils, seashells and crafted tools were found dispersed through many regions. This greater pool of resources led to increased innovation, says Shogren.”

and:

“Shogren tested his theory with simulations of population growth. He even gave the Neanderthals, who were larger than Homo sapiens, a head start by assuming they were better hunters and individually brought home more meat – which may or may not be true.

But because humans were allowed to trade, in two of three similar simulations, they overcame this initial handicap and ousted the Neanderthals within 7000 years. In the third simulation, the two ended up co-existing.”

I hasten to say, that I am not convinced. Many theories have been proposed for the extinction of the neanderthals. Among them this theory climing cold temperatures killed them off (even though most paleoanthropologists see a lot of “cold adapted” traits in neanderthal anatomy).