Study differentiates facial growth in Neanderthals and modern humans

NYU-led research differentiates facial growth in Neanderthals and modern humans
Growth directions of the maxilla in the Sima de los Huesos (SH) and Neanderthals compared to modern humans. This impacts facial growth in at least two ways. (i) Extensive bone deposits over the maxilla in the fossils are consistent with a strong forward growth component (purple arrows); whereas resorption in the modern human face attenuates forward displacement (blue arrow). (ii) Deposition combined with larger developing nasal cavities in the fossils displaces the dentition forward generating the retromolar space characteristic of Neanderthals and also in some SH fossils. Credit: Rodrigo S Lacruz

An international research team, led by Rodrigo Lacruz, PhD, assistant professor in the Department of Basic Science and Craniofacial Biology at New York University's College of Dentistry (NYUCD), has just published a study describing for the first time the developmental processes that differentiate Neanderthal facial skeletons from those of modern humans.

Lacruz's research team showed that the Neanderthals, who appeared about 200,000 years ago, are quite distinct from Homo sapiens (humans) in the manner in which their faces grow, adding to an old but important debate concerning the separation of these two groups. The paper, "Ontogeny of the Maxilla in Neanderthals and their Ancestors," appears in Nature Communications

"This is an important piece of the puzzle of evolution," says Lacruz, a paleoanthropologist and enamel biologist. "Some have thought that Neanderthals and humans should not be considered distinct branches of the human family tree. However, our findings, based upon facial growth patterns, indicate they are indeed sufficiently distinct from one another.

In conducting the research, the team set out to understand the morphological processes that distinguish Neanderthals' faces from modern humans'—a potentially important factor in understanding the process of evolution from archaic to modern humans.

Bone is formed through a process of bone deposition by osteoblasts (bone-forming cells) and resorption by osteoclast (bone-absorbing) cells, which break down bone. In humans, the outermost layer of bone in the face consists of large resorptive fields, but in Neanderthals, the opposite is true: In the outermost layer of bone, there is extensive bone deposition.

The team used an electron microscope and a portable confocal microscope, developed by co-author Dr. Timothy Bromage of NYUCD's Department of Biomaterials, himself a pioneer in the study of facial growth remodeling in fossil hominins, to map for the first time the bone-cell growth processes (resorption and deposition) that had taken place in the outer layer of the facial skeletons of young Neanderthals.

NYU-led research differentiates facial growth in Neanderthals and modern humans
Scanning electron microscope images show details of bone microanatomy. Scale bars, 100 mm. (a) Bone-forming surfaces are relatively smooth, presenting collagen deposits by osteoblast cells. Image taken on the maxillary bone of the Devil's Tower Neanderthal. (b) Resorption is identified as irregular surfaces carved by osteoclasts on the bone surface as they dissolve and remove bone matrix. Image taken from the maxillary bone of the SH hominin Cranium 16. Credit: Rodrigo S Lacruz
"Cellular processes relating to growth are preserved on the bones," says Bromage. "Resorption can be seen as crater-like structures—called lacunae—on the bone surface, whereas layers of osteoblast deposits have a relatively smooth appearance."

The study found that in Neanderthals, facial bone-growth remodeling—the process by which bone is deposited and reabsorbed, forming and shaping the adult skeleton—contributed to the development of a projecting (prognathic) maxilla (upper jawbone) because of extensive deposits by osteoblasts without a compensatory resorption—a process they shared with ancient hominins. This process is in stark contrast to that in human children, whose faces grow with a counter-balance action mediated by resorption taking place especially in the lower part of the face, leading to a flatter jaw relative to Neanderthals.

The team studied several well-preserved Neanderthal child skulls unearthed in 1926 in the British territory of Gibraltar and from the La Quina site in southwestern France, also excavated in the early 1900s. They also compared Neanderthal facial-growth remodeling with that of four Middle Pleistocene (about 400,000 years ago) hominin faces of teenagers from the fossil collection of the Sima de los Huesos in north-central Spain. The Sima fossils are considered likely Neanderthal ancestors based on both anatomical features and genomic DNA analysis.

"We always considered Neanderthals to be a very different category of hominin," said Lacruz. "But in fact they share with older African hominins a similar facial growth pattern. It's actually humans who are developmentally derived, meaning that humans deviated from the ancestral pattern. In that sense, the face that is unique is the modern human face, and the next phase of research is to identify how and when modern humans acquired their facial-growth development plan."

Moreover, Lacruz says, understanding the process of facial ontogeny can help explain the variation in facial size and shape among modern humans.


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More information: Rodrigo S. Lacruz et al. Ontogeny of the maxilla in Neanderthals and their ancestors, Nature Communications (2015). DOI: 10.1038/ncomms9996
Journal information: Nature Communications

Citation: Study differentiates facial growth in Neanderthals and modern humans (2015, December 7) retrieved 20 June 2019 from https://phys.org/news/2015-12-neanderthals-intriguing-difference.html
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Dec 07, 2015
Well, maybe the researchers should read phys.org:

http://phys.org/n...nce.html

The article discusses the difference between Neanderthal and Human faces are due to an evolution of skull and facial features that are more resistant to breakage, and thus can handle a fistfight.

"What we found was that the bones that suffer the highest rates of fracture in fights are the same parts of the skull that exhibited the greatest increase in robusticity during the evolution of basal hominins. These bones are also the parts of the skull that show the greatest difference between males and females in both australopiths and humans. In other words, male and female faces are different because the parts of the skull that break in fights are bigger in males"

Dec 07, 2015
" how did the development of a small face give rise to typical characteristics of modern humans?"

Neanderthals were cold adapted, and so had evolutionary pressures to not flatten their faces. (Larger sinuses insulate against the cold.)

Anatomically modern humans evolved in a hot climate with larger populations and co-operation. I hear our faces have evolved to be much more dissimilar than in other apes, likely to ease recognition. So that is a possible hypothesis.

@krundolosss: "The article discusses the difference between Neanderthal and Human faces are due to an evolution of skull and and facial features that are more resistant to breakage, and thus can handle a fistfight."

That article discuss nothing of the kind! It discusses Australopithecus vs Homo. Taken at face value, any hypothesis of yours re facial differences in Neanderthals and other humans (Neanderthals were humans too) would be weakened by that article since it groups all Homo in one bin.

Dec 07, 2015
@glenthomastotton: "Smaller faces contribute to the success of modern humans by increasing brain size."

Neanderthals had larger brains than we had. So wrong (doesn't work that way), and wrong (Neanderthals were the ones with larger brains).

Finally, your "whites" example is erroneous racism. Jaw sizes are controlled by both genetics and environment:

- "New research suggests that many of the common orthodontic problems experienced by people in industrialized nations is due to their soft modern diet causing the jaw to grow too short and small relative to the size of their teeth." [ http://www.scienc...2032.htm ]

- " It's impossible to identify a person's ancestry definitively from a single bone." [ http://www.slate....llo.html ]

Dec 07, 2015
I was referencing the other article that I posted a link to, that was on a similar subject of this article that we are commenting on now. Just click the link, read THAT article and you will understand what I am talking about.

Dec 07, 2015
On the subject of racism (yeah I'm going there, LOL), it is undeniable that we even have different races because of evolution. Get mad if you want to, it doesn't matter. Darker skin resists sunlight better (Africans), Closed eyes resist wind better (Asians), White skin and small lips, smaller nostrils resist cold weather better (Europeans, whites). We are animals and we DO adapt to our environment, why would this be offensive?

Dec 07, 2015
Perhaps there is a difference between tooth development between humans who have Jötun genes and those who don't.
Do Negroids have as much impacted wisdom teeth, or juvenile misshapen tooth development as Northern Europeans?

Dec 07, 2015
I am completely unfazed by accusations of Racism. It is just a tactic to shut down honest debate.
If you are ashamed of your race , that's your problem. Suck it up.

Dec 08, 2015
Well, maybe the researchers should read phys.org:

http://phys.org/n...nce.html


Well, maybe you should follow research trends instead of just noting a reference on a casual site and assuming that it's settled science. That one was a crap study and was roundly panned on review. None more so than professional boxers. One trainer of multiple heavy weight contenders said it was the dumbest thing he'd ever read. He mentions many other factors, like balance, that are more important for taking a blow, all factors that were becoming less pronounced at the time that are faces were supposedly evolving to take a blow.

The methodology was rubbish, if you had bothered to read it. It completely fails to recognize the restriction in range in the data, that many of the adaptations had to occur because of other longstanding evolutionary processes. It wasn't even as good as the aquatic ape hypothesis. So, can the attitude, SFB, STFU and read. Silently.

Dec 08, 2015
Egleton 1 / 5 (1) 7 hours ago
I am completely unfazed by accusations


Yeah, it's called being a troll. See also, "oxygen thief", "useless blank".

Dec 08, 2015
You see that attitude with conservative trolls all the time. Being social outcasts, they love to imagine post apocalyptic scenarios or to project the grossest primitivism onto our ancestors all to rationalize their total lack of socialization. They want to believe that inconsiderate, boorish, selfish behavior is more natural than cooperation and empathy. There's an objective measure. Hook a GSR monitor up to one and you'll see big spikes at the mention of the words. Ideas like consideration actually make them cringe. It's a big threat to them. "No, NO, EVERYONE was a selfish boor just like me once upon a time before you LIBRULS ruined it all".

Look on the bright side. You'll never know the abject misery it must be to live in their skin.

Dec 08, 2015
jljenkins 5 / 5 (3) 11 hours ago
crowingmoron 0/5 (100) 12 hours ago
Well, maybe the researchers should read phys.org:
http://phys.org/n...nce.html


Well, maybe you should follow research trends instead of just noting a reference on a casual site and assuming that it's settled science. That one was a crap study and was roundly panned on review.


I can't believe that was taken seriously. If you want to do inductive armchair logic, I think I have a better one saying that pointed faces are rubbish for kissing. Kids make a hominim-like face to kiss without really much kissing. We say that a bad kisser is like "a clam with teeth". All are descriptions of the more typical hominim face. Homo sapiens became more intimate, that led to face to face coitus, tighter family units, post menapausal women serving as nannies, etc. Those were survival advantages and flatter, more kiss amenable faces were selected for. See? MUCH better. Buying?

Dec 14, 2015
Say what you will, I do not insult people in comments sections. If I am misunderstood I will try to correct it. You should try it sometime, perhaps. No insults, just comments.

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