Anthropology 150

THE TRANSITION FROM H. ERECTUS TO ARCHAIC HOMO SAPIENS

In the last lecture we left off with the discussion of Homo erectus and the adaptive

radiation out of Africa.

Remember that Homo erectus was a very long-lived species. It was around for over 1

million years and in that time it accumulated a great many derived traits. Derived traits are

mutations that arise after a species is separated from the last common ancestor shared with

another species. Essentially, derived traits are “new” traits. Traits that are carried over from an

earlier species, and shared among a number of species with a shared ancestor are called

“primitive” traits.

At about 500,000 BP (years before present) Homo erectus begins to accumulate enough

derived traits that the new population can be classified as a different species (that, you will

remember, is the process called anagenesis). That new species is generally referred to as Archaic

Homo sapiens. Archaic Homo sapiens is a descriptive term, not a scientific taxonomic name.

Many prefer a more specific scientific name, such as Homo Heidelbergensis. It could also just

be called Homo sapiens sp. (Which means the species Homo sapiens, without a specified

subspecies). But Archaic Homo sapiens will do for our purposes because we wish to distinguish

these early Homo sapiens from later sub-species, such as Homo sapiens sapiens.

Archaic Homo sapiens (A.h.s.) had a "mosaic" of features. It has some traits that look

like late Homo erectus and some that look like an anatomically modern human (Homo sapiens

sapiens, or AMH to use the convenient acronym). You will remember that last week, in

discussing Homo erectus, I said that the species is very much like us (Homo sapiens sapiens or

Anatomically modern humans, aka AMH) from the neck down, except that most individuals

were more robust. That is, its most distinguishing characteristics of Homo erectus are in the

cranium. It follows that the most distinguishing characteristics of Archaic Homo Sapiens will

also be in the cranium.

Homo erectus is recognized by the flat top of its skull, the prominent brow ridges, and

the almost pentagonal profile of the skull when viewed from the rear. In contrast, Archaic Homo

sapiens has a high and rounded cranial vault like modern humans. The brow ridges are still

there, but are reduced in size, and the front of the face is a little bit flatter (less prognatic) than

Homo erectus. The size of the brow ridges, the degree of prognathism, and the height of the

cranial vault vary by region and population.

The increasing height of the cranium is due in part to the continued enlargement of the

brain. Although late Homo erectus fell within the range of modern humans, the average cranial

capacity was at the low end of the modern spectrum. At the same time the brain was growing,

the jaw was decreasing in size due to a reduction in tooth size. The reduction in tooth size was

probably due to the larger amount of cooked food being eaten. Soft food means that there was no

selective advantage to big molars, and so there was a gradual drift downward. With the front of

the face getting smaller, the only place for the brain to go was up. (Motion studies have shown

that enlarging the cranium to the sides or to the back would have created imbalances when

running).

Fossil examples of Late H. erectus/early Archaic Homo sapiens

Germany: Steinheim ~330 kya Similar to Swanscombe with big brow ridges, rounded back to

the skull and 1150 cc.

Africa: The Broken Hill, Zambia skull ~130 kya -cutmarks on the head (Rhodesian man")

Archaic Homo sapiens Broken Hill, Rhodesia: A mosaic of features

Archaic Homo sapiens Spain: Atapuerca ~350 kya. Several individuals have been found in this

region.The fossil record from Atapuerca (a region that includes the site of Sima de los Huesos) is

lengthy and, as you might expect, the specimens show a great deal of variability. Some look

erectus-like and some look like later Neandertals in their features.

Asia: Solo, Java, Indonesia ~300-100 kya poorly dated ("Solo man"). Changes in culture

The first Archaic Homo sapiens used material culture derived from the Acheulean

technology. They had handaxes and and chopper tools. Later Archaics developed a technology

called Middle Stone Age (the term used in Africa) or Middle Paleolithic (used outside of Africa).

Middle Stone Age (MSA) technology much more specialized than the Acheulean.

Both Acheulean and Oldowan can be described as “core tool” technologies; together they

are called the Lower Paleolithic. In both technologies flakes are removed from a core, and the

core is then the primary tool. In contrast MSA and Middle Paleolithic technologies are centered

on the smaller flakes that are removed from the core. Moreover, the flakes are worked after

removal from the core (through the removal of very small flakes or “retouching”). The fine

reworking of the flakes shaped them into a variety of tool shapes. That is, MSA technologies

produced specialized tools, designed with particular tasks in mind. In contrast, both Oldowan and

Acheulean technologies produced more generalized tools.

Archaeological Sites

Clacton-on-Sea, England ~ 300 kya

Menez-Dregan, France ~ 465 kya

Terra Amata, France ~350 kya (beach hut on the ocean) "Non- utilitarian" behavior Post-

mortem (after death) manipulation of human and animal skulls

Zhoukoudian, China ~ 400 kya Bodo, Ethiopia ~ 600 kya Ornamentation - ocher.

Tool technology

Europe - Wooden spears shaped like a javelin (for throwing?) at 400,000 ya

Prepared core, or "levallois" tool technology (a core is prepared before the last blow, which

requires imagining it) "Flake" tools (small pieces) and possible composite tools (e.g. stone

"hafted" to wood).

The Neandertals

Homo erectus entered Europe soon after 800, 000 BP. The earliest date comes from

Atapuerca Spain, at 780,000 BP. The European population of Homo erectus did very well and

expanded into northern Europe, England, and Scotland by 500,000 BP. The pan-genus transition

from Homo Erectus to Archaic Homo sapiens suggest that the European H. erectus maintained

contact with the rest of the species and that there was gene flow throughout H. erectus and early

H. Sapiens populations.

Soon after 300,000 years ago (after the development of Archaic H. Sapiens) the climate

began to cool. Glaciers moved southward throughout Europe and Asia. In Europe the glaciers

expanded over the Alps and the Pyrenees ranges, isolated the European H. Erectus population.

That population had to survive in western Europe during a glacial maximum.

The Neandertals were the product of the western European Archaic H. Sapiens

population adapting to glacial conditions. The “Classic” Neandertals date form about 150, 000

BP to 25,000 BP. Many of their physical traits are best understood as cold weather adaptations.

Neandertals were short and stocky compared to Archaic H. Sapiens, and to us. This is an

example of Bergman’s rule: stocky bodies preserve heat better, because they maximize body

mass while minimizing suface area. In effect, short stocky bodies preserve body heat better.

Their limb proportions are an example of Allen’s Rule: in cold climates, the length of body

appendages is minimized. In effect, Neandertals demonstrate a combination of Bergman’s Rule

and Allen’s Rule. Their body cores (chest and torso) are larger than Archaic H. Sapiens, while

their arms and legs are shorter. The Neandertals had large noses and sinuses, which functioned to

warm air before it entered the lungs. These features enlarged their faces and made them more

prognathic (forward projecting) than Archaic Homo sapiens.

To counterbalance the forward-projecting face, the Neandertals developed an occipital

bun (a bony mass on the back of the skull). Motion studies by David Lieberman at Harvard have

shown that the counterbalance of the occiptal bun served to kept the head steady while running.

In this way, Neandertals were able to maintain a steady focus on prey as they ran.

The cranial capacity of Neandertals was actually larger (1300 -1640 cc) than that of

modern humans (ca 1300 cc on average). Because of their larger body mass, however, the

Neandertal ratio of mass to brain capacity is equal to that of modern humans.

Neandertal fossils

La Chapelle aux Saints, France Neandertal,

La Ferrasie, France Neandertal:

Skhul V, Israel 35 kya Cultural behaviors

The stone tool industry most closely associated with Neandertals is called the

Mousterian. Mousterian is effectively a Middle Stone Age technology, based upon the

specialized working of flakes.

One distinctive product of the Mousterian technology is the “Levallois flake.” A

Levallois flake is one removed from a carefully prepared core. The final product is removed

from the core with a single blow and yields a beautifully shaped tool with sharp edges around is

margins.

Other Neandertal cultural characteristics

Neandertals buried their dead. Neandertal fossils have been found in prepared pits, or graves.

Neandertals Cared for the old and sick. Many Neandertal fossils show severe injuries,

such as amputations, that would have made it impossible for them to fend for themselves. Those

individuals were nursed back to health and were care for afterwardsMany Neandertal skeletons

show severe injuries that include broken bones. The best modern analogues to those injuries

come from rodeo riders. The suggestion has been made that Neandertals attacked their prey “up

close and personal.” That is, they may have jumped on their prey and dispatched them with

knives, rather than using spears, darts, or traps.

Dental wear patterns (cutmarks visible under the microscope) show they probably held

food with their teeth and then cut it off. They display taurodontism, or an enlarged pulp cavity in

the molar.

Neandertal classification problems

Some physical anthropologists (e.g. Ian Tattersal and Tim White) believe that the

differences between Neandertals and Archaic Homo sapiens is so great that they should be given

a separate species designation (Homo neandertalensis). Others feel that they are just a

distinctive population of Archaic Homo sapiens (Homo sapiens neandertalensis). Recent genetic

studies (see below) suggest that Nendertals were capable of interbreeding with H. Sapiens

sapiens and producing fertile offspring; hence, they belong to the same species.The Late

Neandertals

After 90,000 BP the glacial ice of Europe began to retreat and the Neandertals spread into

Eastern Europe and southwest Asia (the Near East: Lebanon, Syria, Israel, Palestine).

They lived there for tens of thousands of years, although they were highly mobile and did not

reside in one place for long. At the same time, however, another group of hominids was moving

northward out of Africa. This latter group was Homo sapiens sapiens, who are known

colloquially as Anatomically Modern Humans (AMH).

Homo Sapiens Sapiens

For the sake of brevity, I’ll use the term Anatomically Modern Humans (AMH) to refer

to H. Sapiens sapiens.

While the Neandertals were developing in western Europe, archaic Homo sapiens were

having fun elsewhere. The archaeological record of Archaic Homo sapiens is weak in Asia

outside of cave sites, such as Zhoukoudian. So with the exception of that single (but spectacular

site) there is not much to go on. In Africa, however, the record of Archaic Homo sapiens and the

Middle Stone Age is very, very good.

The Powerpoint presentation includes a map of some of the best-known archaeological

sites of the MSA (Middle Stone Age). In recent years, the record has included some finds of

“modern” behavior that twenty years ago was thought to be no older than about 20,000 years.

These behaviors include the creation of art and personal adornments such as jewelry.

Despite increasing cultural complexity, Archaic H. Sapiens faced a crisis of sorts about 200,000

years ago. Environmental degradation reduce human populations to very low levels, perhaps no

more than a few thousand people. Out of this crisis, a new population developed and they are

labelled Homo sapien sapiens, or AMH.

Physical Characteristics of AMH

Some of the distinguishing traits of AMH are continuations of trends begun with Archaic H. Sapiens. These included a higher cranial vault, flatter face, and smaller teeth. One unique trait

of AMH however, is the presence of a notable chin. All archaic H. Sapiens (including

Neandertals) have a receding chin, whereas all AMH (except the British royal family) have

chins.

Distinctive cultural behaviors of AMH

The distinctiveness of AMH behavior has been undermined by the recent discovery of

“modern” behaviors during the MSA. There are, however, trends in behavior that quicken after

the appearance of AMH. These behaviors include1) the use of “Upper Paleolithic” technologies

including blades (stone tools with parallel edges), harpoons, and objects made from bone and

antler. 2) Symbolic behavior, including “art” and personal adornment (beads and other jewelry)

Some have suggested, also, that marks on stones and bone represent a type of notational system,

perhaps for counting or even a calendar.

The use of blades, barbed points (such as harpoons), and the increasing use of bone are

customarily used to define the “Upper Paleolithic.” It is best to think of Upper Paleolithic as a

type of technology, rather than a time period. The reason for that is simply that while AMH are

using their Upper Paleolithic technology, Neandertals are using the Mousterian (a Middle

Paleolithic technology). So, one group is using Middle Paleolithic technology while the other is

using Upper Paleolithic technology. If that is confusing to you, things will get much worse in

just a minute

The Fossil Record of Homo sapiens sapiens

Anatomically modern humans (homo sapiens sapiens) first appear in the fossil record

soon after 200,000 BP. A set of skulls from the site of Herto, Ethiopia dated to about 160,000

BP have undeniably modern traits, including a flat face and a high cranial vault. Soon after,

AMH fossils from Klasies River Mouth and Border Cave (150,000 - 120, 000 BP) have similar

traits. After 100,000 BP the fossil record becomes much larger.

Genetic Evidence for Homo sapiens sapiens

The fossil evidence from Africa is in substantial agreement with genetic evidence for the

initial development of anatomically modern humans. The first genetic study done in 1998 by

Rebecca Cann, Mark Stoneking and Alan Wilson suggested that modern humans developed out

of a population that lived in Africa between 150,000 and 200,000 years ago. This study used

mitochondrial DNA, a type of DNA that occurs outside the nucleus of cells (Mitochondria help

to produce energy for cells). Unlike nuclear DNA, which come from both mother and father,

Mitochrondrial DNA (MtDNA) are passed only through the mother. Thus MtDNA is much

easier to analyze than nuclear DNA. Cann, Stoneking, and Wilson collected MtDNA from living

people with ancestry in different parts of the world. They used a type of statistical cluster

analysis to determine how closely related modern people are to one another. Using a known

event to determine a mutation rate, they calculated that all living people last shared a common

female ancestor about 150,000 years ago and that the common ancestor lived in Africa.

The popular accounts in the press labelled the hypothetical ancestor as the "African Eve" and

their theory of a recent common ancestor became known as the "Eve Hypothesis."

In point of fact, what Cann, Stoneking, and Wilson claimed was all living peoples are

descended from a small population (not necessarily a single woman) that lived in Africa about

150,000 years ago. Although there were some problems with their statistics and their

methodology (they sampled African-Americans rather than modern Africans), their fundamental

conclusions have been confirmed by subsequent studies.

Thus, the fossil record and the genetic analyses are in very close agreement. Despite that

agreement, however, not everyone buys the argument, and there are alternative models

The Multi-Regional Hypothesis

The Multi-Regional Hypothesis has been most forcefully advocatred by Milford

Wolpoff, of the University of Michigan. Wolpoff believes that AMH developed in various

regions throughout the world from populations that go back to the adaptive radiation of Homo

erectus. That is, according to Wolpoff, modern Asians descend from Asian Homo erectus,

Modern Africans descend from African Homo erectus, modern Europeans descend from

Europeand Homo erectus, etc. In this model, there was gene flow between those regional

populations that spread derived traits throughout the world populations of the genus Homo,

effectively keeping everyone moving along the same line of development.

Wolfpoff believes that he can trace certain biological traits from Homo erectus populations up to

modern times in each region. For example, modern Asian populations (and Native Americans)

have a distinctive shape to their incisor teeth, called "shovel-shaped incisors". There is a thick

rim of enamel on the edge of the teeth that give them the appearance of a flat-end shovel.

Wolfpoff identifies that trait in Asian Homo erectus (the Zhoukoudian specimens) and believes

he can trace it all through the fossil records, up to modern Asians.

Few physical anthropologists agree unreservedly with Wolpoff. First, many of the

derived traits he identfies in the regional Homo erectus populations are week. Personally, I don't

see shovel-shaped incisors in the Zhoukoudian specimens. Second, the fossil record in Asia is

almost nonexistant at 100,000 BP, so demonstrating cultural continuity is almost impossible.

Another problem is whether we are looking at homologous traits or analogous traits.

Here, occipital buns are a good example. Neandertals had occipital buns. Many western

Europeans today also have occipital buns. (In the interest of full disclosure, you should know

that I have an occiptal bun). But not all buns are the same. As I mentioned, Daniel Lieberman at

Harvard studied Neandertal crania and found that in that species the occipital bun developed to

counterbalance a prognathic face. What Lieberman found in modern humans, however, is that

the occipital bun is the product of an expanding brain. Modern humans with an occipital bun also

have skulls that are narrow in front (above the eyes). That is, modern humans have an occipital

bun because their skulls are constricted in front: the skull expanded to the back in order to hold

the increasing size of the brain. In short, Lieberman says that occipital buns in modern

Europeans have nothing at all to do with Neandertals and are not evidence of genetic continuity.

Wolpoff’s ideas cannot be accepted without many qualifications, and it is largely

incompatible with the genetic and fossil evidence that AMH originated in Africa. However, the

evidence that AMH interbred with the Neandertals and perhaps other populations such as the

Denosivans, keeps some of Wolpoff’s ideas in play.

The Denosivans

The Denosivans were a population of Archaic Homo sapiens known only from a small

number of fossils. The population was defined by the genetic analysis of a finger bone and a tooth

from Denosiva Cave, in southern Siberia. According to Svaante Paabo, whose laboratory

conducted the analysis, the study of the Denosiva fossils represents the first time that a new

hominin population was defined on the basis of genetic analysis, rather than on the basis of fossil

traits.

The Denosivan genetic analysis supports the hypothesis that Neandertals and Denisovans

were more closely related to one another than either was to modern humans. The analysis

suggests that the Denisons separated from other hominins as long as 700,000 years ago—but

possibly as recently as 170,000 years ago. In either case, the last shared ancestor of Denosivans

and other hominins was an Archaic Homo sapiens of some kind.

Perhaps most importantly, the genetic evidence shows that the genome of the Denisovan

populations survives in modern human populations. The modern indigenous peoples of

Australia and New Guinea may derive up to 6% of their genome from the population to which

the Denisovan fossils belonged. The populations of Melanesian and Polynesia also contain

Denisovan DNA. However, other Asian populations do not contain Denisovan DNA.

In sum, the study of the Denosivan fossils leads to the conclusion that AMH

interbred with at least two populations as they migrated out of Africa: the Neandertals and a

population in Central Asia.

What happened to the Neandertals?

The last Neandertal disappeared by about 25,000 BP, if not earlier. That is, after 25,000

years ago we don't see any fossils with Neandertal traits. What happened to them?

Here are the three primary alternatives

1) Neandertals were pushed to exinction by AMH and their was no significant contact between

the two groups.

2) Neandertals interbred with AMH, so that some of their genome survives today. 3) Neandertals intebred with AMH, but their genome does not survived today either because

they were "genetically swamped" by a larger AMH population or because the offspring were not

fertile. The latter outcome would be because they were so genetically distinct that even if they

had mated, any offspring could not reproduce (in effect, Neandertals and AMH were separate

species).

The Multi-regional hypothesis of Wolpoff would support alternative 2. The "African

Eve" (also called the "Replacement Model") would support Alternative 1 or Alternative 3.

The Neandertal case is the principal data set available to us for testing the alternative hypotheses.

There are actually two data sets available. First is the archaeological and the second is genetic

Archaeology

Neandertals and AMH encountered one another in two settings: Europe and the Near

East. Neandertals expanded into the Near East after 90,000 BP at the same time that AMH was

moving northward out of Africa. But it wasn't until about 40,000 years BP that AMH expanded

beyond the Near East. We can trace that expansion because the Upper Paleotlithic tool kits used

by AMH moves northward and westward. At the same time, the distribution of Mousterian tool

kits used by Neandertals becomes more restricted. Seemingly, AMH is pushing the Neandertals

back into western Europe. It could be, however, that Neandertals are adopting Upper Paleolithic

technologies and that the two populations are interbreeding. In short, the archaeological

evidence is inconclusive and the data are hotly debated. Some archaeologist propose that at

about 50,000 BP the Neandertals of western Europe developed a new type of stone tool

technology, called the Chatelperronian that was quite sophisticated. They see continuity in that

tool technology up to ca. 15,000 BP, well after the Neandertals ceased to exist as a biological

population. Other archaeologists, however, argue that Chatelperronian was invented by AMH as

they reached western Europe. Those debates will not be resolved any time soon, and perhaps are

not resolvable.

The Biological and Genetic Data

Svante Paabo, a scientist at the Max Planck Institute, in Munich, Germany pioneered the

analysis of Neandetal DNA. He and colleagues working at the Max Planck Institute have revolutionized

our understanding of human origins.

Initially, Paabo was able to collect 0.4 grams of a sample from the upper arm bone of a

skeleton found in 1857. In a 1997 study, Paabo compared 378 base pairs of the Neandertal's

mitochondrial DNA to that of modern humans. He found that there were an average of 27

differences between modern and Neandertal DNA. For comparison, the typical variation among

modern humans is just 8 differences. Some interpreted the results to mean that Neandertals are so

vastly different from modern humans that they must be a different species. Others said the results

demonstrated that Neandertals contributed nothing to the modern human genome. Both

interpretations are a bit too strong.

A second study, published in 2010, Paabo and his team analyzed nuclear DNA extracted

from Neandertal fossils and compared it to modern human DNA sequences. They found a

correspondence of 1% to 4% between Neandertals and non-African modern humans. Paabo and

his colleagues deduced from this result that interbreeding between Neandertals and AMH did

occur, and that it took placed outside of Africa, after the AMH diaspora of about 100,000 years

ago but before AMH spread into Asia. They deduced that the Levant is the most likely place

where such inter-breeding took place, and the estimate a date of approximately 100,000 – 60,000

years ago for the contact.

More recent studies have expanded upon the 2010 findings. New ‘hot spots’ for

interbreeding between Neandertals and AMH have been identified within Europe, especially in

northern Italy. Thus, AMH met and interbed with multiple Neandertal populations across wide

distances and at various points in time. These new data, combined with the analysis of the

Denosivan fossils, emphasize that we cannot think about linear succession of hominin species

(e.g., Homo habilis, Homo erectus, Homo sapiens, etc), but must think about different

populations of hominin interacting with one another in complex ways.

Fossil evidence may also support the scenario for interbreeding between Neandertals

and AMH within Europe. The fossil remains of a child from Lagar Velho, have been

interpreted by Joao Zilhao and Erik Trinkaus to show evidence of hybridization between

Neanderthals and AMH. Lagar Velho is a rock-shelter in the Lapedo valley, located about

140 km north of Lisbon, Portugal. The fossilized remains were found in deposits dated by

radiocarbon to about 25,000 years ago. Although the remains are classified as Homo sapiens

sapiens (AMH), the child shows some Neanderthal traits in its skull, and especially in the

proportions of its lower limbs.

Trinkaus believes that if more quantitative analyses of the fossil record were done, as it

was with the Lagar Velho fossil, scholars would find much more evidence of Neandertal traits

surviving in AMH after 25,000 years ago.

Conclusion

The genetic data, in tandem with new fossil evidence and archaeological analyses show

that although Neandertals, and other populations such as the Denosivans, ceased to exist as

distinctive populations by 25,000 years ago, some of their genome survives today. Thus, the

truth seems to be much more complex than either the “Out of Africa” or the “Multi-regonal”

hypotheses would suggest. It seems certain that Homo sapiens sapiens (AMH) encountered

other hominin populations (especially Neandertals) as they migrated out of Africa. In many

cases, it seems that interaction and interbreeding took place. However, it is unlikely that all

interactions were the same. This is a very exciting time to be studying modern human origins

and their interactions with other groups.