Homo neanderthalensis essay

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September 30, 2010

Homo neanderthalensis

Remains of Homo neanderthalensis have been found at sites throughout Europe, as well as in western Asia.  Fossils assigned to this species are also found as far east as Uzbekistan, in Central Asia.  The sites from which this speciess is known, which are predominantly cave sites, date from roughly 150 thousand years ago (ka) to as late as roughly 30 ka.  Homo neanderthalensis displays many unique features, including features in the skull and postcranial skeleton (skeleton minus skull), which are related to their adaptation to hunting large game in cold environments.  Homo neanderthalensis also had sophisticated stone tool technologies designed to hunt large mammals at close range.  This species is important to human evolution because it was contemporary with Homo sapiens and is therefore crucial to our understanding of the origin of our species.

Many of the unique features possessed by H. neanderthalensis are found in the skull.  As with Homo erectus, the general shape of the Homo neanderthalensis skull is long and low with large browridges.  Unlike those of H. erectus, however, the browridges of Homo neanderthalensis form individual arches above each eye orbit.  (The evolutionary significance of heavy brow ridges, called supra orbital tori, is not certain; scientists are confident they did not act as a visor against the sun, did not contribute to the structural strength of the cranium and were not needed as eye protection. Some researchers suggestb they may have been part of a mate recognition system.) In  this way, the Homo neanderthalensis skull resembles that of Homo heidelbergensis. The Homo neanderthalensis skull is quite large, with brain sizes averaging over 1400 cubic centimeters (cc.).  Indeed, the brains of Homo neanderthalensis were bigger than those of Homo sapiens; when judged in relation to body size (see below), however, the brain of Homo neanderthalensis is slightly smaller than that of Homo sapiens.  The middle and lower parts of the  face are positioned far forward relative to the braincase (a condition called “midfacial prognathism”), giving the zygomatics (cheek bones) a “swept back” appearance.  The nasal aperture (hole for the nose) in Homo neanderthalensis is very larger, especially when compared to those of Homo sapiens.  Because the widest point of the cranium (skill minus lower jaw) is across the middle of the braincase, the skull of Homo neanderthalensis is oval-shaped when viewed from behind (the so-called “en bombe” shape).  The braincase also exhibits unique features not found in other hominin species—e.g., occipital buns (thickened, projecting areas at the back of the skull) and suprainiac fossae (small depressions at the back of the skull, just above the occipital bun).   The mandibles (lower jaws) are also large and bear molar teeth with large pulp chambers (the area below the enamel in which nerves and blood vessels reside).

The postcranial skeleton of Homo neanderthalensis also exhibits unique features.  The entire postcranial skeleton is very heavily-built with thick bones.  Individuals were short compared to modern humans; their bodies were also wider, with wider shoulders, rib cages, and hips.  The limb bones were short and the distal segments of the limbs (the bones of the forearm and lower leg) were particularly short.  These features of the postcranial skeleton are similar to those seen in other mammals that live in cold environments.  That is, the skeleton is short and wide to minimize surface area (thereby minimizing heat loss) while maintaining the same mass.

The fossil record of Homo neanderthalensis is very large and this large size has allowed scientists to make interesting inferences about the lifeways of this species using evidence gleaned from the skeleton.  For example, the postcranial skeletons  contain many healed fractures, particularly in the limb bones.  Researchers suggest that these fractures are related to hunting dangerous prey at close range.  

Important inferences can also be drawn from skull fossils of Homo neanderthalensis.  Many scientists argue that the midfacial prognathism found in H. neanderthalensis is an adaptation to counteract strong forces placed on the front teeth during chewing or non-chewing behaviors (e.g., to hold hides while working them).  This hypothesis is consistent with the large degree of wear on the front teeth, which might also indicate the use of these teeth as tools in hide working or other tasks.  Other scientists have suggested that midfacial prognathism was a mechanism to increase the size of the sinuses in order to warm the air in the cold environments in which Homo neanderthalensis lived.  Teeth have also been used to study the growth and development of this speciess.  Some scholars argue that Homo neanderthalensis growth and development was very different than that of Homo sapiens, suggesting that the Homo neanderthalensis did not possess features that are otherwise unique to  Homo sapiens.  Other scientists, however, suggest that these differences are more minor and may overlap with the variation found in modern humans.  These scholars do not exclude the possibility that Homo neanderthalensis shared unique developmental features with Homo sapiens.

Homo neanderthalensis individuals were adept large game hunters and this fact is reflected in the archaeological remains associated with them.  They employed a technique for making stone tools called “prepared-core” or “Leavallois” technique.  This technique involves removing flakes from a core (source rock) in order to produce a flake (a chip of stone removed from a core) of a desired shape.  In particular, chips of stone are removed around the perimeter of the core.  A large flake is then removed from the “prepared” core; the shape of this flake is determined by how the original chips are from the core.  The flake is then sharpened (and resharpened) by removing small flakes on the edges (a technique called “retouching”).  In addition to points, these technique was also used to create other tools—particularly, many different kind of scrapers.  However, Homo neandethalensis also made non-prepared core tools.  Specifically, many late Neanderthal sites contain lithic assemblages (the entire collection of stone artifacts from an archaeological site) that were not made using the prepared-core technique and thus more closely resemble Acheuluean tools.  Distances between the sites where stone tools have been discovered and the location of the source of the raw material used to make the tools—often used as a proxy of the size of the range of hominin species—is greater in Homo neanderthalensis than in Homo erectus, but less than that of Homo sapiens.  This evidence suggests that the ranges of Neanderthal populations were intermediate between those of Homo erectus and Homo sapiens.

Homo neanderthalensis also produced stone tools that closely resemble those made by contemporary Homo sapiens in Europe.  Although some scholars argue that these tools reflect independently innovations, most scientists believe that these tools are evidence that Neanderthals were copying the tools made by H. sapiens.  This position is corroborated by the fact that these tools are normally found at Homo neanderthalensis sites that were close to and contemporary with Homo sapiens sites.  In addition, these tools are almost always produced using the same techniques used by Homo neanderthalensis to make other tools.  In other words, the evidence suggests that Neanderthals made these H. sapiens-like tools using the same techniques they used to make tools prior to the arrival of Homo sapiens.  Thus, it seems more likely that these tools are the result of Homo neanderthalensis copying the end-products of Homo sapiens stone tool technology, rather than an independent invention.

The evidence for symbolic artifacts—e.g., beads, statues, and cave art—are, by and large, absent from Homo neanderthalensis sites.  On the other hand, evidence of symbolic behavior is widespread in Homo sapiens' sites.  Despite skepticism from the majority of workers in the field, some scholars maintain  some Homo neanderthalensis sites bear symbolic artifacts—for example, ochre used for body painting and shell beads.  In addition, there is no good evidence that Homo neanderthalensis buried its dead.  This evidence has led most scientists to accept that, at most, Neanderthals possessed a limited capability for symbolic behavior and this may be linked to limitive cognitive capacity in this species.

Homo neanderthalensis also possessed important adaptations for dealing with the cold environments in which it lived.  For example, Neanderthal cave sites often contain hearths and it is likely that this individuals of this species used animal hides to insulate themselves from cold temperatures.  There is no evidence, however,  Homo neanderthalensis sewed these hides, as no artifacts associated with sewing (e.g., needles and awls) have been found at Neanderthal sites.

Consensus regarding the evolutionary relationships between Homo neanderthalensis and other hominin species has not been reached.  This controversy largely involves the relationship of this taxon and Homo sapiens.  This issue is dealt with in greater detail elsewhere (see essay on Homo sapiens), but the general consensus is that Homo neanderthalensis was a separate species from Homo sapiens and that, although some interbreeding may have occurred, Homo neanderthalensis did not make a lasting genetic contribution to Homo sapiens.