The Tree of LifeThe Tree of Life

QuestionsQuestions

6.5 Billion Humans6.5 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 Did they interbreed with earlier members of the

human family?human family? When did they reach the Americas?When did they reach the Americas?

DNA EvidenceDNA Evidence

Human genome is 99.9% identicalHuman genome is 99.9% identical Random, neutral mutation is marker to Random, neutral mutation is marker to

generational relationshipsgenerational relationships Finding same random marker is indication of Finding same random marker is indication of

shared ancestorshared ancestor Compare markers of different populationsCompare markers of different populations Markers shuffled in sexual reproduction Markers shuffled in sexual reproduction

(combining DNA from Mother and Father)(combining DNA from Mother and Father)

Where is the DNA Evidence?Where is the DNA Evidence?

Mitochondrial DNA (mtDNA) passed intact Mitochondrial DNA (mtDNA) passed intact from mother to childfrom mother to child

Y chromosome passed from Father to SonY chromosome passed from Father to Son

Divergence PointsDivergence Points

5-7 Million Years Ago (MYA)– Divergence 5-7 Million Years Ago (MYA)– Divergence from the Chimpanzee Lineagefrom the Chimpanzee Lineage

4.4+ MYA Ardipithecus Ramidus – first know 4.4+ MYA Ardipithecus Ramidus – first know HominidHominid It is not known if this was part of human descent It is not known if this was part of human descent

chain or even actually bipedal.chain or even actually bipedal. 3.9 – 4.2 MYA Australopithecus Anamensis – 3.9 – 4.2 MYA Australopithecus Anamensis –

Definitely bipedalDefinitely bipedal

From Anamensis to SapiensFrom Anamensis to Sapiens

Australopithecus AnamensisAustralopithecus Anamensis Australopithecus AfarensisAustralopithecus Afarensis Homo HabilusHomo Habilus Homo Erectus – 1.81 – 1.61 MYAHomo Erectus – 1.81 – 1.61 MYA Homo Sapiens Homo Sapiens

Transition Species – 400,000 years agoTransition Species – 400,000 years ago Homo Sapiens Sapiens – 200,000 years agoHomo Sapiens Sapiens – 200,000 years ago Homo Sapiens Neanderthalensis – 200,000 years Homo Sapiens Neanderthalensis – 200,000 years

ago ago

Theory’s of Human EvolutionTheory’s of Human Evolution

1.1. Multi-regional ModelMulti-regional Model H. Sapiens Sapiens transitioned from H. Erectus H. Sapiens Sapiens transitioned from H. Erectus

across a wide portion of Africa and Eurasia.across a wide portion of Africa and Eurasia. Fossil evidence shows that either H. Sapiens Fossil evidence shows that either H. Sapiens

spread very fast after transition or transitioned in spread very fast after transition or transitioned in multiple areas. This is supported by H. Sapiens multiple areas. This is supported by H. Sapiens Sapiens and H. Sapiens Neanderthalensis.Sapiens and H. Sapiens Neanderthalensis.

Genetic exchange across the area would have Genetic exchange across the area would have occurred to accomplish this.occurred to accomplish this.

Theory’s of Human EvolutionTheory’s of Human Evolution

Problems with Multiregional ModelProblems with Multiregional Model Would require persistent and extensive migration Would require persistent and extensive migration

patterns to disperse the necessary genes.patterns to disperse the necessary genes. H. Erectus existed in China and Java for at least H. Erectus existed in China and Java for at least

100,000 years after emergence of H. Sapiens Sapiens 100,000 years after emergence of H. Sapiens Sapiens indicating a slow migration from the transition point.indicating a slow migration from the transition point.

Theory’s of Human EvolutionTheory’s of Human Evolution

2.2. Out of Africa TheoryOut of Africa Theory Noted from the fact that African populations Noted from the fact that African populations

have more differences between themselves than have more differences between themselves than the rest of the human genotypes.the rest of the human genotypes.

It is thought that transition was actually from a It is thought that transition was actually from a small number of individuals.small number of individuals.

Theory’s of Human EvolutionTheory’s of Human Evolution

3.3. Back to Africa Theory Back to Africa Theory Early H. Sapieans transitional forms evolved in Early H. Sapieans transitional forms evolved in

central to west Eurasia, then migrated to Africa central to west Eurasia, then migrated to Africa and hybridized with H. Erectus and other and hybridized with H. Erectus and other hominids.hominids.

The fact that Eurasians are more closely related to The fact that Eurasians are more closely related to each other than to Africans supports this.each other than to Africans supports this.

This transition would still have been from an This transition would still have been from an originally relatively small number of individuals.originally relatively small number of individuals.

Searching for EveSearching for Eve

Mitochondrial DNA TechniqueMitochondrial DNA Technique mtDNA exists outside the cell nucleusmtDNA exists outside the cell nucleus mtDNA is exclusively inherited along the maternal mtDNA is exclusively inherited along the maternal

lineline

Human OriginsHuman Origins

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

mtDNA StudymtDNA Study

A.C. Wilson and R.L. Cann, 'The Recent African A.C. Wilson and R.L. Cann, 'The Recent African Genesis of Humans,' Genesis of Humans,' Scientific AmericanScientific American, April 1992, , April 1992, pp. 68-73 pp. 68-73

Used 100 ethnically diverse individuals.Used 100 ethnically diverse individuals. The common mtDNA ancestral sequence was The common mtDNA ancestral sequence was

coalesced to a “Eve” about 150,000 years ago.coalesced to a “Eve” about 150,000 years ago. Linked through unbroken chain of mothersLinked through unbroken chain of mothers Not necessarily only woman aliveNot necessarily only woman alive

Searching for AdamSearching for Adam

The Y chromosome is exclusively passed thru The Y chromosome is exclusively passed thru the Paternal lineagethe Paternal lineage

The ZFY gene on the Chromosome was The ZFY gene on the Chromosome was picked for a study.picked for a study.

ZFY StudyZFY Study

R. L. Dorit, H. Akashi, and W. Gilbert, R. L. Dorit, H. Akashi, and W. Gilbert, 'Absence of Polymorphism at the 'Absence of Polymorphism at the ZFYZFY Locus Locus on the Human Y Chromosome,' on the Human Y Chromosome,' ScienceScience, vol. , vol. 268, pp. 1183-1185, 1995268, pp. 1183-1185, 1995

Compared 38 men of diverse geographical Compared 38 men of diverse geographical origins.origins.

Their common ZFY ancestral sequence was Their common ZFY ancestral sequence was coalesced to a “Adam” about 270,000 years coalesced to a “Adam” about 270,000 years ago. Also, of African origin.ago. Also, of African origin.

Futher Growth in the TreeFuther Growth in the Tree

Ancestral DNA Markers in San people of Ancestral DNA Markers in San people of Southern Africa and Biaka Pygmies of Central Southern Africa and Biaka Pygmies of Central AfricaAfrica

San have click languageSan have click language Almost certain that small band (1000) humans Almost certain that small band (1000) humans

left Africa for western Asia 50k to 70k years left Africa for western Asia 50k to 70k years ago.ago.

All share unique markersAll share unique markers

Problems with StudiesProblems with Studies mtDNA is 16,000 nucleotides in size.mtDNA is 16,000 nucleotides in size. Human DNA has 6,000,000,000 nucleotidesHuman DNA has 6,000,000,000 nucleotides 400,000 times as much DNA exists which could and 400,000 times as much DNA exists which could and

would have been inherited from other individuals would have been inherited from other individuals than “Eve”.than “Eve”.

mitochondria genes do not normally recombine.mitochondria genes do not normally recombine. They seem to follow the mathematical rules more They seem to follow the mathematical rules more

associated with bacterial genetics than human genetics. 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 chromosomeThe search did not include enough of the chromosome The search had too few starting candidates (as did the The search had too few starting candidates (as did the

“Eve” study).“Eve” study).

PathsPaths

Nile River or Across Red SeaNile River or Across Red Sea One population stalled in Middle EastOne population stalled in Middle East Another migrated toward IndiaAnother migrated toward India ““It was less like a journey and probably more It was less like a journey and probably more

like walking a little farther down the beach to like walking a little farther down the beach to get away from the crowd.”get away from the crowd.”

SW Australia 45k years agoSW Australia 45k years ago 40k years ago contact with Neanderatal. No 40k years ago contact with Neanderatal. No

genetic evidence of cross-breedinggenetic evidence of cross-breeding

Populating the AmericasPopulating the Americas

13k-20k years ago13k-20k years ago Native Americans share markers with AsiansNative Americans share markers with Asians

GenealogyGenealogy

Gene GenealogyGene Genealogy A gradually coalesced towards a unique DNA A gradually coalesced towards a unique DNA

sequence (the root of the tree)sequence (the root of the tree) Individual GenealogyIndividual Genealogy

An increase by a factor of two each generation of An increase by a factor of two each generation of ancestors which contributed to the genetic make-ancestors which contributed to the genetic make-up of the individual.up of the individual.

Human DiversityHuman Diversity

It has been estimated from analysis of the It has been estimated from analysis of the HLA immune genetic complex that human HLA immune genetic complex that human populations have never sunk down below a 50 populations have never sunk down below a 50 or 100 thousand population [Ayala & Escalnte, or 100 thousand population [Ayala & Escalnte, et al1995, p205]. et al1995, p205].

The Genetic make-up of Humans would have The Genetic make-up of Humans would have come from many individuals over the course come from many individuals over the course of many generations, not a single “Eve” or of many generations, not a single “Eve” or “Adam”.“Adam”.

TechnologyTechnology

DNA BarcodingDNA Barcoding mtDNA has fast mutation rate that allows mtDNA has fast mutation rate that allows

differentiation of recent eventsdifferentiation of recent events A 648-A 648-bpbp region of the mitochondrial gene, region of the mitochondrial gene,

known as known as cytochrome cytochrome c c oxidase oxidase II (COI), has (COI), has been proposed as a potential 'barcode'.been proposed as a potential 'barcode'.

FingerprintingFingerprinting

Restrict DNA sample of interestRestrict DNA sample of interest Sort by size using Gel ElectrophoresisSort by size using Gel Electrophoresis Blot DNABlot DNA

VNTRsVNTRs Variable number tandem repeats in intron Variable number tandem repeats in intron

regionregion Blot probed with radioactively label VNTR in Blot probed with radioactively label VNTR in

question. Have either mother or father’squestion. Have either mother or father’s D1, S1 biological offspring. D2 half. S2 D1, S1 biological offspring. D2 half. S2

unrelatedunrelated

Tree of LifeTree of Life

ConclusionConclusion There is not any single individual at this time that could be There is not any single individual at this time that could be

identified as the Mother or Father of the Human race.identified as the Mother or Father of the Human race. We have many genetic Mothers and Fathers however the their We have many genetic Mothers and Fathers however the their

genes have all been jumbled up through generations of sexual genes have all been jumbled up through generations of sexual reproduction.reproduction.

It is possible future techniques “may” allow the discovery of a It is possible future techniques “may” allow the discovery of a genetic “Adam” but it is very likely that this “Adam” might genetic “Adam” but it is very likely that this “Adam” might not be what we consider Human.not be what we consider Human.

It is doubtful that any individual “Eve” could ever be It is doubtful that any individual “Eve” could ever be identified because of the gene scrambling seen thru sexual identified because of the gene scrambling seen thru sexual reproduction.reproduction.