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Why do Neanderthal skulls have such large orbits?

 
 
Reply Mon 30 Jul, 2012 07:43 am
Neanderthal skulls...
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Homo_sapiens_neanderthalensis.jpg/220px-Homo_sapiens_neanderthalensis.jpg
http://mathildasanthropologyblog.files.wordpress.com/2008/08/neander-tabun.gif
http://www-tc.pbs.org/wnet/humanspark/files/2008/07/neanderthal-skull.jpg
http://www.skullsunlimited.com/userfiles/image/variants_large_4478.jpg

Human skull...
http://www.labtechindia.net/product/Biology/bl42.jpg

Please note, I am in no way agreeing with Gunga's recent posts about Danny Vendramini's theory of a Planet of the Apes type nocturnal monster (http://able2know.org/topic/184929-1), but there does seem to be an undeniable tendency toward larger eye sockets, proportionally speaking, in Neanderthal skulls when compared to those of Homo sapiens. Is it worth further discussion?
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Type: Question • Score: 3 • Views: 5,676 • Replies: 16
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DrewDad
 
  1  
Reply Mon 30 Jul, 2012 08:21 am
@iamsam82,
I believe that neanderthal populations were concentrated in higher latitudes.

http://dienekes.blogspot.com/2012/02/big-eye-sockets-compensate-for-low.html

Farmerman should be able to advise whether I am correct....
gungasnake
 
  1  
Reply Mon 30 Jul, 2012 08:35 am
@iamsam82,
There are two possibilities; one of them is a little bit weird, and the other is exceedingly weird..............

The possibility which is just a little bit weird is Vendramini's claim that the Neanderthal had become nocturnal for purposes of hunting. Vendramini also claims that to be nocturnal and yet still be able to function in daylight, a creature with night-vision eyes, particularly huge night-vision eyes as per the Neanderthal, would also need slit pupils and Vendramini assumes they had them. You'd need to somehow reconstruct a Neanderthal (not wise) to check it out...

Another problem is that many if not most dinosaurs had similar large eyes:

http://news.discovery.com/animals/nocturnal-dinosaurs-night-fossil-110414.html

and that included herbivores and flying dinosaurs as well as predators. In our own day and age there are a few monkeys with such eyes but no large herbivores.

The other possibility I mentioned which is significantly more than a little bit weird would nonetheless account for the big eyes in such a number of dissimilar creatures; this is the claim that those creatures never experienced anything which we would call daylight at all.

Read at your own risk...

http://saturndeathcult.com/the-sturn-death-cult-part-1/a-timeless-age-in-a-purple-haze/





0 Replies
 
iamsam82
 
  1  
Reply Mon 30 Jul, 2012 09:09 am
@DrewDad,
DrewDad - They were concentrated in the north, you're right, but the north is not really any darker, is it? During the ice age, when neanderthalensis flourished, the north, cloaked in snow and ice would actually have been exceedingly bright. Homo sapiens suffer snow blindness when exposed to polar regions for any length of time now. I'd imagine a neanderthalensis, with larger eyes letting in even more light, would have been dazzled even quicker in the tundra. So why the large eyes?
Ragman
 
  1  
Reply Mon 30 Jul, 2012 10:13 am
@iamsam82,
http://www.themandus.org/them.html

"what big eyes you have"


"This photo (left), from the book, compares the large optical orbits (eye sockets) of a Neanderthal (left) with those of a human (right). The eyes are considerably larger. According to Vendramini, Neanderthals evolved these extra large eyes because, like most mammalian predators, they were nocturnal hunters.

Slit-shaped pupils are better suited to the eyes of nocturnal primates (right) because they can close down tighter, preventing damage to their super-sensitive eyes from strong sunlight. NP theory argues that, like modern nocturnal predators, Neanderthals had slit-shaped pupils to protect them from snow blindness.

"what's with the eyes?"


Prey species have an innate ability to identify their natural predator in order to effect an escape strategy. Vendramini argues that the distinctive eyes of Neanderthals provided a quick and reliable means of identifying them, so these optical features have been hardwired into our genes. Today, this innate fear is expressed in a universal portrayal of bug eyed monsters in art, mythology and the movies."
farmerman
 
  1  
Reply Mon 30 Jul, 2012 10:20 am
@Ragman,
there is a large varince in neanderthal skulls. ALL have the post orbital structure like we. The superorbital ridges of Neanderthals was much larger than sapiens so this provides a larger orbit opening (Apparent). Also, the orbitals of neanderthals that are exceptionally large are from skulls mostly lacking teetc, indicating age. That apparent large orbital shape is common in sapiens of advanced age when they died
gungasnake
 
  1  
Reply Mon 30 Jul, 2012 10:48 am
@farmerman,
Quote:
there is a large varince in neanderthal skulls. ALL have the post orbital structure like we. The superorbital ridges of Neanderthals was much larger than sapiens so this provides a larger orbit opening (Apparent). Also, the orbitals of neanderthals that are exceptionally large are from skulls mostly lacking teetc, indicating age. That apparent large orbital shape is common in sapiens of advanced age when they died


My father died at age 96 two years ago. His eyes still looked human and not Neanderthal... For that matter from most of what I read at least, lifespan for a Neanderthal was around 40 years and Neanderthal childrens' skulls still show the larger eye openings.
DrewDad
 
  1  
Reply Mon 30 Jul, 2012 10:52 am
@gungasnake,
You boiled all the flesh off of your father's skull?

You're crazier than I thought.
0 Replies
 
Evolutions
 
  1  
Reply Sat 15 Aug, 2015 12:07 pm
@iamsam82,
Neanderthals always puzzled me. They had the largest brain of the hominids and the largest orbits. This leads me to more questions, why did they have such adaptations? Why did our brains shrink after the stage of the Neanderthal?
farmerman
 
  2  
Reply Sat 15 Aug, 2015 12:23 pm
@Evolutions,
we seemed to have missed a popular article about this re: modern humans. It must be recalled that Vendramini only had one or two of the larger orbited skulls. Its from a 2012 article in Sci American

Quote:
Bright-Sized: Skull Study Shows Eye-Sockets Have Grown Larger at Higher Latitudes
Human eyeballs may have grown larger as populations migrated farther and farther from the equator, an eye-socket analysis shows
By Sarah Fecht | February 6, 2012




Wikimedia Commons/Bryan
People who live farther from the equator have larger eye sockets than their tropical counterparts, a new study finds. And as people inhabited higher and higher latitudes, eye socket size grew along with the northerly or southerly extent of their migrations.

"It's never been shown before that latitude and vision are related in this way in humans," says Robert Barton, an evolutionary anthropologist from Durham University in England, who was not involved in the research.

The experimental design was quite simple. The researchers studied a museum collection of 73 healthy 200-year-old skulls from 12 different populations. For each skull, they lined an eye socket (which anthropologists call the "orbit") with laboratory film and filled it with small glass beads to measure the volume. Then they charted the location where each skull was dug up, and calculated average light levels for each locale, based on its latitude and longitude. It turned out that skull orbits obtained from higher latitudes held more glass beads: Those from nearer to the equator held 22.5 milliliters, on average, whereas the ones from inhabitants living more than 40 degrees north or south of the equator held closer to 27 milliliters.

"Days are shorter as you move away from the equator, and the duration of dawn and dusk increases," explains Eiluned Pearce, a University of Oxford doctoral student who co-authored the paper with her advisor, evolutionary anthropologist Robin Dunbar. Because of the diminished light, Pearce and Dunbar hypothesized that humans at higher latitudes would need to develop specialized visual systems to continue to be able to spot predators and recognize social cues from other humans.

The implications of the report, published in the February issue of Biology Letters, are not completely surprising. A few years ago, ecologist Robert Thomas of Cardiff University in Wales found that songbirds with larger eyes sing at lower daily light levels (such as at dawn and dusk) than do birds with smaller eyes—presumably because animals with larger eyes have larger pupils which funnel more light into the eye, thereby increasing the length of activities associated with daylight. "We all imagine people as a bit different from animals and maybe not subject to the evolutionary circumstances," Thomas says, "but here's a fantastic example of the evolutionary process working on human societies that live in different places."

However, it is risky to use eye-socket volume as a proxy for eyeball size, cautions physical anthropologist Christopher Kirk from the University of Texas at Austin. The actual eyeball takes up less than one third of the volume of the socket—the rest of it is filled with fat, muscle and connective tissue. One alternate explanation is that humans at higher latitudes require larger eye sockets to accommodate larger fat pads to act as insulation in colder weather. Other factors such as chewing muscles, the shape of the nasal cavity and the size of the frontal lobe also influence eye-socket size and shape. For these reasons and more, it would be best to measure eyeballs themselves, Kirk says.

And that is exactly what Pearce is working on now. With the help of a network of researchers, she is collecting and analyzing MRI scans from all over the world, in order to measure the eyeball sizes of modern populations and to determine how exactly they vary with latitude. At this point, it is not clear whether the eye-socket volume is genetically heritable or if it develops over an individual's lifetime. "This seems to be the first time anyone has ever really thought about this, so this paper was really about putting that hypothesis out there," Pearce says. There's still a lot of work to be done and many questions to be answered.

"For some reason, orbit size increases with latitude," Kirk says. "That's a phenomenon that needs to be explained."
Evolutions
 
  1  
Reply Sat 15 Aug, 2015 12:38 pm
@farmerman,
I had no idea latitude differed orbit size. So it was an adaptation they had received, since dawn and dusk was longer farther away from the equator. I still don't understand the purpose of their brain size and why we don't have one like theirs.
farmerman
 
  1  
Reply Sat 15 Aug, 2015 12:48 pm
@Evolutions,
Ive also heard that the Neanderthals were "cropuscular" rather than nocturnal or diurnal. Why? maybe predation, who knows.
Also Ive been told that a larger part of the frontal lobes of Neanderthals were sensory related (Smell and sight) so the larger bucket capacity was maybe sensory functional and not intellect related
Evolutions
 
  2  
Reply Sat 15 Aug, 2015 12:57 pm
@farmerman,
I like the evidence on them being corpuscular. The time when the nocturnal animals just awake and the diurnal go to sleep. The perfect time for predation. You are most likely right about the frontal lobes being sensory, if that whole brain was dedicated to whits they'd be smarter then today's scientists.
0 Replies
 
Ragman
 
  1  
Reply Sat 15 Aug, 2015 01:48 pm
Not to be too nitpicky..but that word is "Crepuscular".
farmerman
 
  1  
Reply Sun 16 Aug, 2015 05:07 am
@Ragman,
Hey, Im just wingin it. If you didnt jump in, Ill bet we coulda hd that word evolve into something totally indecipherable (check my spelling on that)

Ragman
 
  1  
Reply Sun 16 Aug, 2015 06:11 am
@farmerman,
Understand that I'm not being critical. Your spelling and typing has improved a lot - not that you needed me to say it. I dare say it's pretty easy to read these days.

Back to the topic, has it been determined that size of the brain is 100% a determiner about what we call intelligence? Isn't there some correlation between density (?) and/or amount of convolutions or wrinkles?

I'll use this excerpt to express where I was trying to go:

"Scientists have been divided about what they're measuring and how they're measuring it. Anthropologists have long used a skull's interior volume and compared it against body size for a rough estimate of intelligence, measurements known as encephalization quotients. As brain-imaging techniques have improved, though, scientists have measured actual brains with greater precision. But is it size or is it neurons that we need to measure? Is it weight or circumference? Should encephalization quotients use total body weight or lean body mass? Should we correct for body size at all? How do you measure intelligence?"

Furthermore, Smithsonian Magazine has something to say on the subject:
http://www.smithsonianmag.com/science-nature/why-brain-size-doesnt-correlate-with-intelligence-180947627/?no-ist
Ragman
 
  2  
Reply Sun 16 Aug, 2015 06:30 am
@Ragman,
Specifics from that Smithsonian Magazine article:

"People have long been tempted to link brain size and cognition. The intuitive notion that a “big brain” means “more intelligent” was first threatened some time ago, when we discovered animals with larger brains than ours: elephants and whales. Sure as we were of humankind’s superior intelligence, we still felt the need to prevail, so we gamely parried: Perhaps it is the brain size relative to body size that makes our brains the biggest. Though humans come out well there, too, this measure is biased toward birds and other small animals that have relatively large brains for their bodies. After more deliberation, scientists finally offered up the so-called “encephalization quotient”: brain size relative to the expected brain size in related taxa. On top: humans. Phew.

Consider, though, the strange case of that growing child. Every infant’s brain develops through a period of synaptogenesis—wanton proliferation of synapses, which are the connections between neurons—in the first year or so of life. But one could argue that it is when this intense brain growth ends that the real growth of the child qua individual begins. The next phase of brain development occurs in large part through an increase in synaptic pruning: paring of those connections that are not useful for perceiving, considering or understanding the world the child is facing. In this sense, it’s by downsizing that an individual’s brain is born.

Brain size, or the size of brain parts, can be a reasonable indicator of skill, to be sure. In individuals with sensory deprivation other sensory inputs take over the cortical area lying dormant. In the case of blindness, auditory or tactile somato-sensory areas may grow in size, and hearing or touching sensitivity will improve accordingly. Dramatic as that compensatory growth may be, in the end the correlation between brain size and brain function is fraught.

Consider the humble dog, Canis familiaris. The brain of a wolf-size dog is about 30 percent smaller than that of an actual gray wolf, its ancestor. Has the dog become less smart since it went its own evolutionary way thousands of years ago? Judge for yourself: When the mere gaze from the dewy eyes of a member of this species causes you to get up from the couch, repair to the refrigerator and retrieve a hunk of cheese for your charge—well, you tell me who is smarter.
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