Evolution of hominin intelligence

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The evolution of hominin intelligence can be viewed as a result of an environmental challenge throughout time and can be traced over the past 10 million years. There are several ways to define intelligence besides the more common measure of "understanding". Intelligence includes a combination of traits such as reasoning, planning, the comprehension of ideas, language, learning and problem solving. More sophisticated qualities of intelligence that are very difficult to quantify include creativity or personality traits.

Development of the brain

It is believed that the size of the brain determines the intelligence of the individual(2), The beginning of the Pliocene is where we begin to notice the development of the hominin brain(2) before this time period, the hominin brain was no larger then the brain of other mammals of similar size. Early hominin had an excellent understanding of the mechanical properties and increase in cognitive adaptability. Compared to chimpanzees and gorillas, the development of the hominin brain is three times larger. Current research on the HAR1(Human Accelerated Region 1) has quickly evolved in the modern hominin’s compared to their ancestors(8). HAR1 is an RNA gene that is expressed in the early neural embryo genesis. Through re-sequencing studies, David Hausler et.al indicated that the changes in the human lineage to be approximately more then 1million years old(3). HAR1 encodes for two oppositely transcribe RNA’s; 1) HAR1F and 2) HAR1R. David Hausler observed that the double-stranded helix of the HAR1F is longer in modern humans compared to chimpanzees. This suggests that RNA on the brain is different in hominin compared to chimpanzee and gorillas. Also, Stern and Woods state that both genes Microcephalin (MCPH1) and ASPM (MCH 5) control growth of brain size. However, more studies are needed for the HAR 1, MCPH1 and MCH5.

A larger skull created a problem for the female hominin’s because it requires the female to have a larger birth canal. A larger and wider pelvis would lose her ability to use the other motor skills(7) that were used for survival. The mother had to give birth at an early stage otherwise the infant skull grew too large for the birth canal. This suggests the dependency that the hominin infants have to their mothers compared to other mammal and primate infants. With the need to care for infants, hominin groups were force to stay in one location for long periods of time. This suggests the increase of dependency on tool-making because male hominin’s would hunt and defend his area, while the female hominin’s would care for area.

http://anthro.palomar.edu/hominid/images/pelvis_and_feet.gif

Pleistocene (1.8million years)

Pleistocene (1.8mya to 10 Ka) was the beginning of the evolution of modern humans, Stone-age culture and technical complexity. Australopithecus are related to hominin’s but during this time period, the hominin brain size increased, which suggest the increase of intelligence. Approximately 2mya, Homo habilis showed characteristic of modern hominin. Evidence of tool-making, such as stone, teeth and claws from other animals were used which gave evidence that hominin diet increased from herbivore to carnivore. Understanding the use of stone tool allowed early hominin such as Homo habilis to cut hide and meat, thus increasing their understanding and ability to adapt to their environment. However, more research is still needed to the understanding of the hominin diet.

Stone tool

Diversity of tool-making and tool-using behavior is observed in chimpanzee but the intelligence of advance stone tool is observed from early hominid. The use of stone tools required larger brain mass to complete such skill to survive. With the understanding of tools and the ability to control fire, this gave early hominin the ability to defend themselves against predators, allow longer hours to gather and hunt for food. The earliest evidence of hominin technology is found in Ethiopian Rift Valley and the Olduvai Gorge, dated 2.5 Mya. Known as the Oldowan Industrial Complex, Australopithecus Africanus and Homo habilis are considered to be the first tool maker, were highly skilled in stone flaking (1). Unlike, chimpanzee’s that have a narrow fingertip, most hominins have short straight fingers and long thumb that increases the stability of gripping tools. Homo habilis is considered to be the first tool maker. Around 1.5 mya, large cutting tools of approximately 10 to 17 cm long were invented by Homo erectus, thus developing the Acheulean industrial complex. Large cutting tools suggests that these tools were multipurpose tools, such as butchery, woodworking, etc. (1)

Homo habilis, Homo erectus,and Neanderthal Man

Homo habilis

Australopithecus evolved bipedal; however, hominids developed a variety of things that we use today such as culture, art, religion, language and tools. The first species to appear in the genus Homos is Homo habilis, which evolved around 2mya. The skull is thinner and more rounded, which suggests intelligence and lager brain mass. Even though their cranial capacity (600 to 800 cc) and body size was about half of Modern Man, their hands and feet are similar in size to that of “Homo sapien sapiens” . Less prominent jaw, small teeth compared to body size and artifacts that were found with the fossil, which suggest that they utilized and advanced stone flakes for tool-making (1). It is observed that Homo habilis used tools for cleaving meat off and for scavenging.

Homo erectus

Homo erectus was more diverse and developed better tools and weapons. Highly sexual dimorphic, their brain size is approximately 950cc, while their height was 5’10” (males). Believed to be the first human species of hunter-gatherer society, their cranial capacity suggests more sophisticated tool technology (1). It is also believed that Homo erectus is the first to be able to hunt on a large scale, tame fire, and live in small societies, while caring for others.

Location of the Discover of Homo erectus

Name: Java Man Discovered: Eugene Duboise Location: Sangrian,Java

Name: Peking Man Discovered: Davidson Black Location: Zhoukoudian,China

Name: Africa Discovered: Richard Leakey Location: Lake Turkana Olduvai Gorge

Neanderthal man

Also known as Homo sapiens neanderthalensis, "Neanderthal man" is believed to have coexisted with modern humans after Homo sapiens migrated to Europe (6) Similar height to modern man, "Neanderthal man" had a short robust body, larger brain capacity, and large nose. The height of the male is approximately 5’5” and the female was 5’0”. It is suggested that their use tool-making were of the Mousterian class, where their hammers were made from material such as bones, antlers and wood, rather then just a stone hammer.

Reference

1. Ambrose SH (2001) “Paleolithic Technology and Human Evolution.” Science Volume 291, pages 1748-1753

2. Flinn MV, Geary DC, Ward CV (2005) “Ecological dominance, social competition, and coalitionary arms races: Why humans evolved extraordinary intelligence.” Evolution and Human Behavior Volume 26, pages 10-46

3. Goymer P, (2006) “ RNA on the brain makes us different” Nature Volume 7, page 680

4. Klein RG (2003) “Paleoanthropology: Whither the Neanderthals?” Science 299 Page 1525-1527

5. Mcilroy, Anne (2006) Neanderthal may have lived longer then thought. Globe and mail. Retreived on 2008-03-24

6. Pollard KS et. al “An RNA gene expressed during cortical development evolved rapidly in humans” Nature Volume 441, pages 167-172

7. Rosenberg KR, Trevathan W. (1996) "Bipedalism and human birth: the obstetrical dilemma revisited" Evolution Anthropology Volume4, page 161-168

8. Stern R, Woods CG (2006) “Is brain evolution still continuing un modern human” European Journal of Human Genetics Volume 14, pages 799-800