The Tree of Life

Questions 6.5 Billion Humans 6.5 Billion Humans Who were the first modern people in Africa? Who were the first modern people in Africa? Why did humans leave Africa 50,000 years ago? Why did humans leave Africa 50,000 years ago? What routes did they take? What routes did they take? Did they interbreed with earlier members of the human family? Did they interbreed with earlier members of the human family? When did they reach the Americas? When did they reach the Americas?

DNA Evidence Human genome is 99.9% identical Human genome is 99.9% identical Random, neutral mutation is marker to generational relationships Random, neutral mutation is marker to generational relationships Finding same random marker is indication of shared ancestor Finding same random marker is indication of shared ancestor Compare markers of different populations Compare markers of different populations Markers shuffled in sexual reproduction (combining DNA from Mother and Father) Markers shuffled in sexual reproduction (combining DNA from Mother and Father)

Where is the DNA Evidence? Mitochondrial DNA (mtDNA) passed intact from mother to child Mitochondrial DNA (mtDNA) passed intact from mother to child Y chromosome passed from Father to Son Y chromosome passed from Father to Son

Divergence Points 5-7 Million Years Ago (MYA)– Divergence from the Chimpanzee Lineage 5-7 Million Years Ago (MYA)– Divergence from the Chimpanzee Lineage 4.4+ MYA Ardipithecus Ramidus – first know Hominid 4.4+ MYA Ardipithecus Ramidus – first know Hominid It is not known if this was part of human descent chain or even actually bipedal. It is not known if this was part of human descent chain or even actually bipedal. 3.9 – 4.2 MYA Australopithecus Anamensis – Definitely bipedal 3.9 – 4.2 MYA Australopithecus Anamensis – Definitely bipedal

From Anamensis to Sapiens Australopithecus Anamensis Australopithecus Anamensis Australopithecus Afarensis Australopithecus Afarensis Homo Habilus Homo Habilus Homo Erectus – 1.81 – 1.61 MYA Homo Erectus – 1.81 – 1.61 MYA Homo Sapiens Homo Sapiens Transition Species – 400,000 years ago Transition Species – 400,000 years ago Homo Sapiens Sapiens – 200,000 years ago Homo Sapiens Sapiens – 200,000 years ago Homo Sapiens Neanderthalensis – 200,000 years ago Homo Sapiens Neanderthalensis – 200,000 years ago

Theory’s of Human Evolution 1. Multi-regional Model H. Sapiens Sapiens transitioned from H. Erectus across a wide portion of Africa and Eurasia. H. Sapiens Sapiens transitioned from H. Erectus across a wide portion of Africa and Eurasia. Fossil evidence shows that either H. Sapiens spread very fast after transition or transitioned in multiple areas. This is supported by H. Sapiens Sapiens and H. Sapiens Neanderthalensis. Fossil evidence shows that either H. Sapiens spread very fast after transition or transitioned in multiple areas. This is supported by H. Sapiens Sapiens and H. Sapiens Neanderthalensis. Genetic exchange across the area would have occurred to accomplish this. Genetic exchange across the area would have occurred to accomplish this.

Theory’s of Human Evolution Problems with Multiregional Model Problems with Multiregional Model Would require persistent and extensive migration patterns to disperse the necessary genes. Would require persistent and extensive migration patterns to disperse the necessary genes. H. Erectus existed in China and Java for at least 100,000 years after emergence of H. Sapiens Sapiens indicating a slow migration from the transition point. H. Erectus existed in China and Java for at least 100,000 years after emergence of H. Sapiens Sapiens indicating a slow migration from the transition point.

Theory’s of Human Evolution 2. Out of Africa Theory Noted from the fact that African populations have more differences between themselves than the rest of the human genotypes. Noted from the fact that African populations have more differences between themselves than the rest of the human genotypes. It is thought that transition was actually from a small number of individuals. It is thought that transition was actually from a small number of individuals.

Theory’s of Human Evolution 3. Back to Africa Theory Early H. Sapieans transitional forms evolved in central to west Eurasia, then migrated to Africa and hybridized with H. Erectus and other hominids. Early H. Sapieans transitional forms evolved in central to west Eurasia, then migrated to Africa and hybridized with H. Erectus and other hominids. The fact that Eurasians are more closely related to each other than to Africans supports this. The fact that Eurasians are more closely related to each other than to Africans supports this. This transition would still have been from an originally relatively small number of individuals. This transition would still have been from an originally relatively small number of individuals.

Searching for Eve Mitochondrial DNA Technique Mitochondrial DNA Technique mtDNA exists outside the cell nucleus mtDNA exists outside the cell nucleus mtDNA is exclusively inherited along the maternal line mtDNA is exclusively inherited along the maternal line

Human Origins Allan Wilson at Cal-Berkeley in 1980s Allan Wilson at Cal-Berkeley in 1980s Used mtDNA to identify Used mtDNA to identify African women show 2x as much diversity African women show 2x as much diversity Humans lived in Africa 2x as anywhere else Humans lived in Africa 2x as anywhere else Based on steady rate of random mutations Based on steady rate of random mutations

mtDNA Study A.C. Wilson and R.L. Cann, 'The Recent African Genesis of Humans,' Scientific American, April 1992, pp A.C. Wilson and R.L. Cann, 'The Recent African Genesis of Humans,' Scientific American, April 1992, pp Used 100 ethnically diverse individuals. Used 100 ethnically diverse individuals. The common mtDNA ancestral sequence was coalesced to a “Eve” about 150,000 years ago. The common mtDNA ancestral sequence was coalesced to a “Eve” about 150,000 years ago. Linked through unbroken chain of mothers Linked through unbroken chain of mothers Not necessarily only woman alive Not necessarily only woman alive

Searching for Adam The Y chromosome is exclusively passed thru the Paternal lineage The Y chromosome is exclusively passed thru the Paternal lineage The ZFY gene on the Chromosome was picked for a study. The ZFY gene on the Chromosome was picked for a study.

ZFY Study R. L. Dorit, H. Akashi, and W. Gilbert, 'Absence of Polymorphism at the ZFY Locus on the Human Y Chromosome,' Science, vol. 268, pp , 1995 R. L. Dorit, H. Akashi, and W. Gilbert, 'Absence of Polymorphism at the ZFY Locus on the Human Y Chromosome,' Science, vol. 268, pp , 1995 Compared 38 men of diverse geographical origins. Compared 38 men of diverse geographical origins. Their common ZFY ancestral sequence was coalesced to a “Adam” about 270,000 years ago. Also, of African origin. Their common ZFY ancestral sequence was coalesced to a “Adam” about 270,000 years ago. Also, of African origin.

Futher Growth in the Tree Ancestral DNA Markers in San people of Southern Africa and Biaka Pygmies of Central Africa Ancestral DNA Markers in San people of Southern Africa and Biaka Pygmies of Central Africa San have click language San have click language Almost certain that small band (1000) humans left Africa for western Asia 50k to 70k years ago. Almost certain that small band (1000) humans left Africa for western Asia 50k to 70k years ago. All share unique markers All share unique markers

Problems with Studies mtDNA is 16,000 nucleotides in size. mtDNA is 16,000 nucleotides in size. Human DNA has 6,000,000,000 nucleotides Human DNA has 6,000,000,000 nucleotides 400,000 times as much DNA exists which could and would have been inherited from other individuals than “Eve”. 400,000 times as much DNA exists which could and would have been inherited from other individuals than “Eve”. mitochondria genes do not normally recombine. mitochondria genes do not normally recombine. They seem to follow the mathematical rules more associated with bacterial genetics than human genetics. They seem to follow the mathematical rules more associated with bacterial genetics than human genetics. Flaws can be demonstrated in the search for “Adam”. Flaws can be demonstrated in the search for “Adam”. The search did not include enough of the chromosome The search did not include enough of the chromosome The search had too few starting candidates (as did the “Eve” study). The search had too few starting candidates (as did the “Eve” study).

Paths Nile River or Across Red Sea Nile River or Across Red Sea One population stalled in Middle East One population stalled in Middle East Another migrated toward India Another migrated toward India “It was less like a journey and probably more like walking a little farther down the beach to get away from the crowd.” “It was less like a journey and probably more like walking a little farther down the beach to get away from the crowd.” SW Australia 45k years ago SW Australia 45k years ago 40k years ago contact with Neanderatal. No genetic evidence of cross-breeding 40k years ago contact with Neanderatal. No genetic evidence of cross-breeding

Populating the Americas 13k-20k years ago 13k-20k years ago Native Americans share markers with Asians Native Americans share markers with Asians

Genealogy Gene Genealogy Gene Genealogy A gradually coalesced towards a unique DNA sequence (the root of the tree) A gradually coalesced towards a unique DNA sequence (the root of the tree) Individual Genealogy Individual Genealogy An increase by a factor of two each generation of ancestors which contributed to the genetic make- up of the individual. An increase by a factor of two each generation of ancestors which contributed to the genetic make- up of the individual.

Human Diversity It has been estimated from analysis of the HLA immune genetic complex that human populations have never sunk down below a 50 or 100 thousand population [Ayala & Escalnte, et al1995, p205]. It has been estimated from analysis of the HLA immune genetic complex that human populations have never sunk down below a 50 or 100 thousand population [Ayala & Escalnte, et al1995, p205]. The Genetic make-up of Humans would have come from many individuals over the course of many generations, not a single “Eve” or “Adam”. The Genetic make-up of Humans would have come from many individuals over the course of many generations, not a single “Eve” or “Adam”.

Technology DNA Barcoding DNA Barcoding mtDNA has fast mutation rate that allows differentiation of recent events mtDNA has fast mutation rate that allows differentiation of recent events A 648-bp region of the mitochondrial gene, known as cytochrome c oxidase I (COI), has been proposed as a potential 'barcode'. A 648-bp region of the mitochondrial gene, known as cytochrome c oxidase I (COI), has been proposed as a potential 'barcode'.bpcytochrome c oxidase Ibpcytochrome c oxidase I

Fingerprinting Restrict DNA sample of interest Restrict DNA sample of interest Sort by size using Gel Electrophoresis Sort by size using Gel Electrophoresis Blot DNA Blot DNA

VNTRs Variable number tandem repeats in intron region Variable number tandem repeats in intron region Blot probed with radioactively label VNTR in question. Have either mother or father’s Blot probed with radioactively label VNTR in question. Have either mother or father’s D1, S1 biological offspring. D2 half. S2 unrelated D1, S1 biological offspring. D2 half. S2 unrelated

Tree of Life

Conclusion There is not any single individual at this time that could be identified as the Mother or Father of the Human race. There is not any single individual at this time that could be identified as the Mother or Father of the Human race. We have many genetic Mothers and Fathers however the their genes have all been jumbled up through generations of sexual reproduction. We have many genetic Mothers and Fathers however the their genes have all been jumbled up through generations of sexual reproduction. It is possible future techniques “may” allow the discovery of a genetic “Adam” but it is very likely that this “Adam” might not be what we consider Human. It is possible future techniques “may” allow the discovery of a genetic “Adam” but it is very likely that this “Adam” might not be what we consider Human. It is doubtful that any individual “Eve” could ever be identified because of the gene scrambling seen thru sexual reproduction. It is doubtful that any individual “Eve” could ever be identified because of the gene scrambling seen thru sexual reproduction.