The Out of Africa theory believes that anatomically modern humans evolved in Africa and then migrated into Eurasia replacing all populations that were descendants from Homo erectus.
Key points to this theory are: t
- There were two migrations out of Africa and after the first wave were Homo erectus migrated out populations became isolated, evolved independently and even evolved into separate species (Templeton, 2002).
- The separate species that progressed from this isolation was that of the H. neanderthalensis. H. neanderthalensis fossils have Robust limb bones, large rounded cranial vaults and skulls with projecting jaws and were found throughout Europe and Asia (Wood & Collard, 1999).
- Staying in Africa and evolving there were Homo sapiens. They too like the others migrated out of Africa and then according to this theory, replaced all other human populations without interbreeding.
Templeton, A. (2002). Out of Africa again and again. Nature, 416(6876), 45-51.
Wood, B., & Collard, M. (1999). The human genus. Science, 284(5411), 65-71.
US National Library of Medicine http://ghr.nlm.nih.gov/chromosome/MT
Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA. Mitochondrial DNA is the genetic material found within the mitochondria in humans. It spans about 16,500 DNA building blocks (base pairs), representing a small fraction of the total DNA in cells.
Many genetic conditions are related to changes in particular mitochondrial genes including cancer of the breast, colon, stomach, liver and kidney. It may also be related to leukemia and lymphoma. Other disorders that can be caused from changes in mitochondrial genes are cyclic vomiting syndrome, cytochrome c oxidase deficiency , Kearns-Sayre syndrome , Leber hereditary optic neuropathy , Leigh syndrome , maternally inherited diabetes and deafness , mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes, myoclonic epilepsy with ragged-red fibers , neuropathy, ataxia, and retinitis pigmentosa , nonsyndromic deafness , Pearson marrow-pancreas syndrome and progressive external ophthalmoplegia.