Evolution of the World

One million years after Lucy, some hominin species develop larger brains and start showing signs of Human intelligence by making tools. As a result, we start including the word Homo (human) in their names, like Homo Sapiens for us. Earlier hominins, like Lucy, are called Australopithecus (southern Ape) - "A." for short, as shown in the usual DIAGRAM of evolution !

Although these smarter hominins most certainly used other materials like wood, animal skin and bone; the only tools to survive from that time are those made of stone. As a result, "History" enters the Stone Age or Paleolithic era.

- 2.5 Mya:   Homo_habilis [ Wikipedia ]

The first tool user, named Homo Habilis, appears around 2.5 Mya. He was short (~150cm) and looked like an ape ( appearance ); but, whereas apes and older hominins had used whole stones to crack nuts, Habilis started splitting stones with one or two blows to get flakes with a sharp cutting edge. The original stone core left behind would serve as a scrapper.
The Habilis technique is called "Oldowan" [Reference] and their simple tools are labelled "mode 1" . Oldowan tools were sufficient for Habilis since he was mainly vegetarian, only occasionally eating scavenged meat scraped off bones.

Habilis survives for half a million years, co-existing for a time with his successor, Erectus.

- 2 Mya:  Homo erectus [ Nature Education ].

Next, a new more "human" species appears. He has a bigger body and brain [ Ref. ] and a modern upright stance which leads anthropologists to call him Homo erectus. Physically, H. Erectus is the first hominin to look like modern man ( appearance ).
See also: Palomar College

Homo Erectus is a most interesting ancestor.

1. He stays around - in various forms - for more than 1.5 million years. This makes Homo erectus by far the longest lasting species of all our relatives. Check

2. Erectus also stands out as the first of our ancestors to be discovered.
   - Erectus remains, estimated to be over 700,000 years old, were uncovered in 1891, on the island of Java. The bones, part of a skull and a tibia, denoted a species halfway between Ape and modern Man. Java Man, in the words of the Press, became the first piece of evidence for human evolution.

3. In addition, Erectus demonstrated Human intelligence by developing a sophisticated, and easily recognizable, technique to obtain sharp edges on stone tools. Emblematic of this "Acheulean" technique was the hand axe, a thin teardrop shaped cutting tool in regular use for over a half million years [ Illustration ].

4. Finally, more curious and mobile than his predecessors, Erectus migrates Out of Africa and spreads over 3 continents - as shown in green below.

NOTE: In spite of this wide ranging migration, the global population of early hominin species before the arrival of Homo Sapiens is estimated to have remained below 100,000 individuals.

Spread of Erectus

We now know that Erectus originated in the Rift Valley of East Africa around 2 Mya. Soon thereafter, the species expanded out of Africa, reaching Dmanisi (Georgia) around 1.8 Mya; then pushing eastward through the Middle East, to get to China and Indonesia around 1.7 Mya.

Historically, this "Out of Africa" sequence of events was not obvious because all the really old fossils were initially discovered in Asia. When Java Man ( ~700 Ky old ) was found in Indonesia, our only other known ancestor was a contemporary of early Sapiens, a 40 Ky old Neanderthal found in Germany. The next few discoveries, starting with Peking Man, found just north of Beijing in 1921, all came from either China or Indonesia. This gave rise to the theory that early man had originated in Asia.

It was only after 1960, that field work by Louis Leakey and others in East Africa established Africa as the true spawning ground for successive hominin species. [Ref: Smithsonian, also Facts&Details ]. Initially, the Leakeys found trace of the older Homo habilis in the Rift Valley; then, Erectus remains dating back to 1.4 Mya were uncovered at Olduvai Gorge in Tanzania; and even older remains were found, by others, in Ethiopia (2.3 Mya). In addition, Turkana Boy, a nearly complete skeleton dating back 1.9 Mya, was found in northern Kenya and a skull dated to 1.95 Mya uncovered in South Africa.

Evidence of Erectus in Europe would come a few decades later.

• 1983: remains of 30 hominins dated 400 Kya were found in Atapuerca (Spain)
• 1991, skulls dated 1.9 Mya were uncovered in Dmanisi (Georgia)
• 1994: more remains, dated between 780,000 and 1.2 Mya, found in Atapuerca [ Wikipedia ].
• 2013: an even older human fossil dated 1.4 Mya was found at Orce in Andalusia.

Click HERE for more details on these discoveries and a dated MAP of migration

Note: Erectus presence in Europe will treated more fully in the next section.

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Erectus Evolution

During his 1.5 million year presence, Erectus underwent significant evolution. Physically, over time, Erectus grew taller and in northern areas developed a stockier body. But, the most obvious changes occurred in the size and shape of the head. This allowed the brain to more than double in size getting close to that of modern man (1400 cc).

Our distant cousin, the chimpanzee has a brain size around 400 cc. Erectus started in Africa with a slightly bigger brain, around 600 cc, similar to his predecessor, Habilis; but reaching 1250 cc in his later period in Europe as H. Heidelbergensis. This is shown in the table and illustration below:

There was also a change in the shape of the skull. Early hominins - like modern apes - have a large jaw and an elongated skull, much like an american football. They also have a pronounced eyebrow ridge and a sloping forehead. Later hominins have smaller jaws and more spherical skulls. Click the image at right for a larger view and other images.

Note: SEE HERE the vertical forehead and protruding chin that characterize Sapiens .

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Erectus "species"

Traditionally, Erectus evolution has been presented as a succession of overlapping "species", including: H. ergaster, H. rudolphensis and H. heidelbergensis with H. erectus reserved for the Asian specimens.

The reason for this is that Erectus evolution occurred in a distributed manner with small groups isolated for extended periods, and fossils all differ in small ways... except that skull size tends to increase over time.

As a result, deciding whether new finds represent different species, breeds or individuals is often a matter of debate amongst experts [ see The Species Debate or Lumpers vs Splitters]. Anthropologists often refer to the Erectus period as the Muddle in the Middle .

Only later, around 300 Kya in Europe, do we find sets of remains that obviously belong to the same species: like the Neanderthals.

Presently, the "species" pointed out above are considered to be geographic variants: Ergaster refers to smaller early Erectus found in Africa, Dmanisi - first variant to leave Africa -, and Heidelgergensis applies to the latest incarnation which moved north, adapted to the colder weather and evolved into the Neanderthals and the Denisovans in Asia. In Africa, Heidelgergensis mutated in Homo Sapiens around 300 Kya.

Intelligence

A bigger brain is not necessarily a more intelligent brain; but Erectus shows intelligent behaviour in many ways:

• Extensive migration requires advanced skills to survive in a multitude of environments: like the ability to hunt, fashion traps and shelters, transport food, water and babies over large distances, etc...
• The Acheulean technique developed for stone tools like hand axes relies on sequences of blows in specific places with exactly the right force and angle to achieve sharp bifacial edges. The process takes time, and requires training, dexterity and foresight: demonstrating a sophisticated level of thinking [Video]. Acheulean is also called "mode 2" technology.
  Note: the name "hand AXE" is misleading since these were never designed to chop wood; rather they served as a prehistoric SWISS army knife: used to dig for roots, scrape meat off carcasses, crack open bones, etc....
• Finally, recent discovery of Erectus artifacts on Flores, a remote Indonesian island, indicates that Erectus had developped seafaring skills by 800 Kya. Basically, the only way to reach Flores was by a series of sea channel crossings, each requiring several hours, paddling a raft accross current [ see Prehistoric Craft or NZ Encyclopedia ]. This also supports the Gibraltar crossing as the initial route out of Africa into Europe.

However, H. Erectus had limits:

• Art: Erectus left no drawings or decoration - indicators of abstract thought.
• Speech: His ability for modern speech was limited by the lack of our vocal structures as well as the speech gene found in modern humans. However, transmission of technology implies communication skills beyond grunting [ Ref ].
• Fire: Erectus learned to maintain fire and use it to cook food; but starting fire, would have to wait for the Neanderthals.

End of Erectus

Thus, in the West, Erectus "disappears" around 600 Kya, mutating into more advanced versions [Ref: Wikipedia Fossils ].

In the East, Erectus does not evolve and dies out: around 400 Kya in China, and a bit later, ~ 100 Kya, in Indonesia [ Ref ]. One isolated island group, the Flores "hobbits," - thought to be descendants of early Erectus navigators who underwent Island Dwarfism over time - survived until 50,000 years ago only to be wiped out by the arrival of Sapiens.

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"Biocultural" Evolution

With Erectus, a new mode of "Biocultural" evolution comes into play: where biological change combines with the development of technology and communication to make a species increasingly successful at acquiring food and surviving predators [ Ref. D. O'Neil ].

With sharp tools and better weapons, Man will rise to the top of the food chain without the necessity of evolving claws. Later, with fire and the use of animal skins as clothing, we will be able to survive in northern climates without evolving body fat and fur.

In what follows, we will be less concerned with the biology of "species" and more with evolving mental capacity and the increasing use of acquired knowledge. However, the process still takes time. Bigger brains will need to evolve specialized areas for language and abstract thought. Inventions need smart inventors to be born and stumble on the right idea. Then, these ideas have to spread from group to group. The next major milestones in evolution include :

In the next section, we will be less concerned with biological evolution and more with evolving mental capacity and the increasing use of acquired knowledge.

References

• Atlas of Human Evolution: The Age of Homo Erectus
  
• List of Hominin Fossils ( Wikipedia )
• Lumpers and splitters
• DNA and Evolution, molecular clock
• Anthropology Tutorials by Dennis O'Neill, Palomar College
• Evolution - Historical Geology, large... takes time to open
• Hominin Skulls

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