- Darwin didn’t really apply evolution to humans
the science at that time placed severe limits on the time available to happen for evolution - 1858: Thompson (Lord Kelvin) said Earth was around 100 million years old
he used calculations for time required for Earth to cool
Rutherford later found that it was 4.5 billion years because of radioactive decay - Finally, Darwin published The expression of the Emotions in Man and Animals Natural Selection in Human Evolution
- Recall the importance of diversity to finches - Our species is also diverse (homo sapiens)
- Some paleoarchaeologists say that there used to be many human species
- Our species evolved over time and was also the only surviving descendant of the hominid line (we were competitively superior to the other human species)
- You many ask, what are the characteristics that made our line so successful?
History of the Homonid Line
- The ancestral branching of our species is unclear
- 4.4 million years ago in Africa, there lived an early hominid Ardipithecus ramidus
after them there were 2 species similar to us:
Australopithecus anamensis and Australopithecus afarensis
they were like us because of bipedalism: the ability to move about the environment upright on two feet
these species showed the ape-like ability to climb trees - 3 to 2 million years ago, the hominid line split in 2
- This may be due to the African environment become drier, making changes in the food source - The two lines were
1) genus Paranthropus, with powerful jaws to crush plants and nuts 2) continued from Australopithecus
- 2.5 to 1.8 million years ago, there were 2 distinct new species that made the genus Homo: Homo ruddfensis, Homo habilis (means handy man because of stone tools)
Tools = Advantage
- Homo habilis had an advantage if they really used stone tools
- By then, there were 4 homonid species in East Africa, and so tools meant an advantage for food competition
- By then, hominids showed encephalization: an increase in brain size
bigger brains = more metabolic energy = tolls needed to get more calories - But the use of the stone tools is still unclear
it could be for raising their children
it could be that they carried their tools to scavenge meals opportunistically New Tools: A Certain Kind of Technology
- 1.8 million years ago, hominids left Africa - Homo erectus was found as far as java and China
- They used tools where they chipped at larger stones until they became a hand axe - 600 000 years ago, Africa, Homo heidelbergensis planned more for their tools
they made it so a well directed blow would detach the finished tool
- From them came the last 2 major hominid groups: Homoneanderthalensis (Neanderthals) and Homo sapiens
- We originated in Africa 150 000 – 200 000 years ago and lived with the Neanderthals for awhile - Two characteristics of us that natural selection favored: bipedalism (greater mobility, use of
hands) and encephalization (learning, remembering skills, tool making, escaping predators) The Need for Encephalization
- You may think, the Paranthropus hominids adapted to their drier environment by having stronger jaws, it makes sense
- But why did we all of a sudden, develop a larger brain?
- 1993: Dunbar said that Homo species were in an environment that favored large groups
a large brain is then needed to remember things that underlie all social interactions
he found that encephalization was correlated with the typical size of that species’ social group
according to this relationship, then the typical group size of modern humans is 148
- Large brains may have been our advantage because it helped us to coordinate socially and meet environmental challenges as a group
- As the brain got larger, more and more of it became for organizing social life
memorizing actions (hunting and tool production)
linguistic ability
manipulating symbols
planning (hunts, social customs, planting/harvesting crops) Language
- Tool making and hunting advances, and the use of fire all helped humans survive longer - There was more wisdom in the older members
- Eventually, the wisdom was passed on to younger members through language - From then on, language evolved because it was so adaptively significant
use it to warm others of danger
to communicate information like good hunting spots, how to make a tool
language reinforced the strong social tendencies of the early humans - Dunbar said that language replaced grooming behavior
- Language probably then led to cultural traditions Neanderthals vs. Homo sapiens
- Neanderthals became extinct 25 000 years ago - Homo sapiens have survived for 200 000 years
- The two species overlapped and it’s unclear if there was interbreeding - Neanderthals had a cultural tradition, they used symbols in art
- Culture has adapted over the years Cultural Evolution
- Cultural evolution: the adaptive changes of cultures in response to environmental changes over time
agricultural revolution, Industrial Revolution, technological revolution
cultural evolution is only possible because humans have the capacity for learning and language - Cultural evolution, unfortunately, leads to pollution, social ills/injustices (racism), and
overpopulation
Evolution of our Capacity for Learning
- Harris says that our capacity for learning has also evolved, and so it allows 1) more flexible and faster way to have reproductive success
2) groups of people can adjust in one generation without waiting for genetic mutation
we now have cures for many diseases so we don’t have to wait many years for us to become immune to it
Sociobiology
- Sociobiology: the study of the genetic bases of social behavior
it is related to evolutionary psychology and behavior genetics, which are more broad
sociobiology looks at social behavior as well as things like intelligence, cognition
they try to understand evolutionary roots of our modern day social actions
they first study animals, then extrapolate to humans
sociobiology is the line between psychology and biological science - One thing that sociobiologists study is reproductive strategies and parenting