Deep time refers to an enormous timescale with which geologists and scholars of evolution must deal. Homo sapiens first emerged as a separate species, not 800 years ago, or even 10,000 years ago, but somewhere between 100 and 200 thousand years ago. The earliest identifiable human ancestor appeared between 7 and 6 million years ago. And the earliest primates occurred between 65 and 55 million years ago. The planet itself if 4.6 billion years old.
These timescales can be hard to get your head around but they are pivotal to understanding the overall story of life on earth.
Physical evidence of human ancestors (and other forms of prehistoric life) comes primarily from the fossil record. Fossils consist of the remains of once-living organisms that have been preserved through a natural process whereby the organic tissue is replaced with minerals from the surrounding environment. In short, they turn into rock.
Fossilization is a very selective process.
Only a small fraction of living organisms become fossilized. Conditions that lead to fossilization are just too rare.
Second, even when fossilization occurs, often not the whole creature becomes fossilized. It is technically possible for soft tissues to be fossilized, but it is extraordinarily rare. Far more often, what we find are the larger and denser bones of the body. Thus for human ancestors, we have found lots of teeth and skulls, along with some long bones and pelvises, but very few ribs and bones from the hands. These bones are just too small and fragile to regularly withstand the fossilization process. An additional challenge to the fossil record is that paleoanthropologists have to actually find the fossils!
Paleoanthropology has found a powerful new source of information—Genetic Analysis! The Mitochondrial Eve study.
Mitochondrial DNA mtDNA is found only in your mitochondria (small organelles inside of your cells). Replacement Thoery
Out of Africa Theory
How does the Theory of Evolution Explain the Diversity of Life? There are four principle forces to evolution
Mutation, Natural Selection, Gene Drift, and Gene Flow
Define and describe them
Physical anthropologists have boiled genus homo down to four principle traits: Bipedalism
Walking on two feet instead of four (i.e. quadrapedalism)
Expanded brain capacity and complexity
Global Migration - Human beings, largely through their use of culture (particularly material culture) have expanded to all corners of the globe. No other species has been able to do that.
What has Made Modern Humans so Successful at Survival?
Where did Variations in Human Skin Color Come From?
The Role of Ultraviolet Light- Vitamin D Hypothesis
Vitamin D is a vitally necessary nutrient for healthy bone growth. A lack of vitamin D can lead to rickets in children and other diseases in adults, all of which can be fatal. However, exposure to too much UV light can also have negative consequences to the human body. Exposure to UV light destroys folic acid, which is particularly important during fetal development. Thus, low levels of folic acid in pregnant women can lead to significant, and even fatal, birth defects. Melanin and Melanocytes
Define and how do the work
Relevance to Genetic Adaption and the deconstruction of race as biological Clines
Chapter 6: Introduction to Race and Racism
Anthropological view of Race
Race as a Flawed Concept
What is meant by Fuzzy Boundaries in a Well-Integrated Gene Pool? Clines
The Wild Goose Chase: Linking Phenotype to Genotype
How are racial classifications cultural?
How is Race Constructed Around the World?
Race and the Legacy of Colonialism
Other Racial Classifications:
The Dominican Republic
How is Race Constructed in the United States?
History of U.S. Racial Categories
The Rule of Hypodescent
Race and Immigration