Whither the Neanderthals.docx

8/14/2019 Whither the Neanderthals.docx

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Whither the Neanderthals?

Neanderthals-

Longest known and best understood of fossil humansFirst partial skeleton discovered in 1856 in Germany

Today, thousands of Neanderthal bones are known from more than 70 sitesDespite this, paleoanthropologists still cant decide how Neanderthals were

different from living humans, or why they disappeared

Most Neanderthal bones are isolated skeletal parts- mostly teeth and jaws

Nearly every part of the skeleton is represented in multiple copies

More than 20 partial skeletons from both sexes and different ages

More than 300 archaeological sites have yielded artifacts and animal bones

illuminating Neanderthal behavior

Neanderthals evolved in Europe

Distinctive anatomical features mark European fossils that are more than 350,000years old

Through natural selection and genetic drift, Neanderthals appeared about 130,000

years ago

Distributed continuously from Spain to southern Russia

By 80,000 years ago, they had gone into western Asia

They persisted there until about 50,000 years ago

In some places until 30,000 years ago

Neanderthals were the predecessors of modern humans

Suggested that they were ancestors of living populations

When the Neanderthals occupied Europe & Western Asia, other peoples lived in theFar East & Africa

The Africans were anatomically more modern than the Neanderthals

Variants of mtDNA and the Y-chromosome in living Eurasian humans derive from

African variants

Further support- from mtDNA extracted from Neanderthal bones

Shows that the last shared ancestor of Neanderthals & humans lived 500,000-

600,000 years ago

Non-sex chromosomes of humans may retain some Neanderthal genes

Fossil & genetic evidence suggests that Neanderthal contributions to living

populations is small

Modern humans invaded west Asian Neanderthal range about 45,000 years ago

They swept north and west through Europe, overtaking the Neanderthals within 10-

15,000 years

Modern humans were technologically, economically and demographically more

advantaged- greater ability to innovate


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Physically-

Neanderthals had large heads, large trunks, and short/powerful limbs

Average brain size = or > modern humans

Skulls exhibit specializationsForward projection of the face along the midline

Braincase bulged outwards at the sides

Depressed elliptical area of roughened bone on the back of the skull

Many bumps and crannies in the mastoid process

High activity levels and strenuous lifestyle explain the powerful limbs

The short limbs and large trunk conserved body head- probably an adaptive

response to the glacial conditions at the time

Modern successors- Cro-MagnonsDiscovered in 1868

Neanderthal bones occur with artifacts from the Middle Paleolithic

Cro-Magnon bones occur with artifacts from the Upper Paleolithic

Middle & Upper Paleolithic people shared many advanced behaviors

Refined ability to flak stone

Burial of dead

Interest in mineral pigments

Control over fire

Dependence on meats

Neanderthals and Cro-Magnons skeletons sometimes show disabilities- showingthat they cared for the old and sick

Differences

Neanderthals left little evidence of art or jewelry

Smaller range of stone tool types

Rarely crafted artifacts from bone, ivory, shell, or antler

No evidence of projectile weapons


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Didnt built lasting structures

Confined to mild & temperate latitudes

What they produced varied little

Cro-Magnons were much more varied

ContactRadiocarbon dating suggests that Cro-Magnons displaced the Neanderthals about

45,000 years ago in W. Asia and only about 5-15,000 years ago in Europe

There may be contaminations that make these dates wrong

Only the alternation of Neanderthal and Cro-Magnon layers within one site could

provide unarguable evidence of an overlap doesnt exist yet

The implication is that in more places the Neanderthals disappeared abruptly

Neanderthal & Cro-Magnon interbreeding has been suggested from occasional

fossils

Including a childs skeleton found in Portugal

In each case, the anatomical indications are ambiguousEvidence for cultural contact is sparse, except for one case from France-

A site occupied by Neanderthals before their disappearance

Provided a mix of Middle & Upper Paleolithic artifacts

Including Bone tools & Jewelry

The only indisputable house ruin from a Neanderthal site

Could mean that Neanderthals could imitate Upper Paleolithic neighbors

Cognition & Extinction

Except for the French site, there is little evidence that the Neanderthals could have

existed like the Cro-Magnons did

This may explain why they disappeared so quicklyNeanderthal brains werent any smaller than human brains

If there was a difference in brain function, it was in soft disuse that cant be inferredfrom empty skulls

So neither archaeology nor fossils can reveal Neanderthal cognitive capacity

This issue is also important because

Fossils show that between 130-50,000 years ago, African contemporaries of the

Neanderthals were more modern in anatomy

But archaeology suggests that they resembled the Neanderthals in behavior

A change in brain function about 50,000 years ago could explain why the Africans

expanded to Eurasia

The discovery of the FOXP2 gene

Involved in speech and language

Achieved its modern sequences less than 200,000 years ago

Provides tentative support for change in brain structure/function

Many human gene variants are very ancient


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But if there was a brain change, one or more variants should coalesce about this

time

Fossil bones could provide a further test- some have been shown to retain organic

compounds bearing on brain function

Longest debate in paleoanthropologyModern humans replaced the Neanderthals with little/no gene exchange

Neanderthals succumbed because they didnt use culture as effectively

Do Neanderthal genes explain their failure? Will they?

Manual Dexterity

Despite the fact that Neanderthals could make/use stone tools, they were presumed

to have limited manual dexterity

This has been questioned

Examined this using a 3 dimensional simulation based on the anatomical details of

the thumb and index finger of NeanderthalsThe digits could make tip-to-tip contact

Epoxy casts of the La Ferrassie 1 Neanderthal thumb and index-finger bones were

scanned

Produced a 3 dimensional polygon mesh model of the bones

These models generate a computer model that simulates movement and

motion

A specific bone- the metacarpal-1 base (the pads of the thumb and fingers)- is a key

feature used to grip things precisely

The analysis indicates that some Neanderthal metacarpal-1 bases are morecondyloid shaped

But the La Ferrassie Neanderthal seems more developed- making it likely that the

range of movement for its trapezial-metacarpal joint is similar to modern humans

Actually, because the Neanderthal joints have a more open configuration, its likelythat their thumbs were more mobile than modern humans

It has been suggested that their thumb movements were restricted, so they

minimized the mobility of the thumb by using the middle range of human values

Also examined the index finger movement

This has a lot to do with the asymmetry of the index-finger knuckle joint, whichcauses the finger to flex

Neanderthal kuckles are apparently les asymmetrical than modern humans

But the modern human flexion/extension values and joints are functionally

equivalent in Neanderthals and modern humans

Even allowing for limited joint movements in modern humans, the flexing of thumb

and index finger allows for tip-to-tip contact


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One study suggested that the Neanderthals short thumb and first-finger could have

inhibited their precision of movement

This study indicated that this wasnt true

There is no significant difference between Neanderthals and Modern humans in the

locations of their muscle and ligamentous attachments

Thus there remains no anatomical argument that precludes modern-human-likemovement of the thumb and index finger in Neanderthals

The demise of the Neanderthals cant be attributed to any physical inability to use ormanufacture Upper-Palaeolithic-like tools

According to the evidence, they were capable of manufacturing and handling such

implements

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