1. Chapter 17 Topics 17-1 Human Origins 17-2 Fossil Evidence 17-3 Hypotheses of Hominid Evolution

2. Human Classification  Kingdom Animalia Animalia  Phylum Chordata Chordata  Subphylum Vertebrata Vertebrata  Class Mammalia Mammalia  Order Primates Primates  Family Hominidae Hominidae  Genus Homo Homo  Species sapiens sapiens

3. Hominid Fossil Record  Hominids – subgroup of primates that includes humans and bipedal ancestors  Paleoanthropologists study hominid fossils for clues to evolutionary events: Curvature of spine Curvature of spine Attachment of spine to skull Attachment of spine to skull Skull: shape & size, teeth Skull: shape & size, teeth Pelvis shape Pelvis shape  Other areas of interest include: Tools found near fossil remains Tools found near fossil remains Fossil remains of plants, pollen, animals near hominid fossils Fossil remains of plants, pollen, animals near hominid fossils

4. Primate Characteristics  Primates composed of 2 groups: Prosimian primates – lemurs, lorises, tarsiers Prosimian primates – lemurs, lorises, tarsiers Anthropoid primates – monkeys, apes, humans, marmosets Anthropoid primates – monkeys, apes, humans, marmosets  Anthropoid primates characterized by: Opposable thumb & non-human anthropoids have an opposable toe Opposable thumb & non-human anthropoids have an opposable toe Collarbone Collarbone Rotating shoulder joint Rotating shoulder joint Partially rotating elbow joint Partially rotating elbow joint Dental formula: 2 incisors, 1 canine, 2 premolars, 3 molars (each side up & down) Dental formula: 2 incisors, 1 canine, 2 premolars, 3 molars (each side up & down) Cranial capacity large in relation to body size, used to estimate brain size Cranial capacity large in relation to body size, used to estimate brain size  Humans characterized by: Bipedalism Bipedalism Spine – 2 curves Spine – 2 curves Foot adapted to bipedalism Foot adapted to bipedalism Cranial capacity large Cranial capacity large

5. Prosimian Primates  http://www.cvm.missouri.edu/SCAAZV/lem urs.htm http://www.cvm.missouri.edu/SCAAZV/lem urs.htm http://www.cvm.missouri.edu/SCAAZV/lem urs.htm

6. Anthropoid Primates  www.getahead.psu.edu/AnthropoidEvol utionG.html www.getahead.psu.edu/AnthropoidEvol utionG.html www.getahead.psu.edu/AnthropoidEvol utionG.html

7. First Hominids  Evolutionary theory does NOT espouse that “man evolved from apes”. Rather, there was a common ancestor from which apes and man descended Rather, there was a common ancestor from which apes and man descended  Traits defining hominid line: Bipedalism Bipedalism Large cranial capacity for higher reasoning & speech Large cranial capacity for higher reasoning & speech  Fossil evidence for 2 hominid genuses Australopithecus Australopithecus Homo Homo  Bipedalism evident ~ 3.6MYA, predates cranial enlargement

8. Genus Australopithecus  A. afarensis (named after the Afar Valley in which she was found) “Lucy” was discovered in 1974 “Lucy” was discovered in 1974 3.2 M years old 3.2 M years old 1.5m tall, 475cm 3 brain (human brain 1400cm 3 ), bipedal, female 1.5m tall, 475cm 3 brain (human brain 1400cm 3 ), bipedal, female  A. africanus dates from 2.3 – 3 MYA  A. robustus dates from 1.5 MYA  A. bosei dates from 2.5 – 3.75 MYA  A. anamensis

9. Hominid Skull Capacity

10. Hominid Evolution Time Chart

11. Genus Homo  H. habilis thought to have arisen from the A. afarensis lineage as an “offshoot”  Look at the Homo lineage chart in the previous slide  Why is it that the lines are not connected?

12. Homo sapiens  All humans are Homo sapiens Species – a group of similar organisms that produce fertile offspring Species – a group of similar organisms that produce fertile offspring  Humans have a variety of phenotypes, but surprisingly, human genotypes are very similar. Why is that?  Two theories are: Multiregional Evolution Hypothesis Multiregional Evolution Hypothesis Recent African-Origin Hypothesis Recent African-Origin Hypothesis

13. Multiregional Hypothesis  Humans evolved all over Earth in parallel from different populations of H. erectus This assumes that these separate populations must have gene flow constantly between them This assumes that these separate populations must have gene flow constantly between them Constant gene flow would be necessary to keep the populations uniform Constant gene flow would be necessary to keep the populations uniform  Usually populations that are separated, tend to speciate due to specific environmental pressures (think about Darwin’s finches)  Currently, this hypothesis not widely accepted

14. Recent-African-Origin Hypothesis  Modern Homo sapiens originated in Africa about 100,000 -200,000 YA & then left Africa  Homo erectus & early Homo sapiens like Neanderthals, were displaced by these migrating Homo sapiens, & so, died out  Evidence supported by “mitochondrial Eve”

15. “Mitochondrial Eve” Our Most Common Recent Ancestor  Mitochondria – originated from small aerobic prokaryotes living w/i larger cells A symbiotic relationship developed between the anaerobic host cells as they became increasingly dependent upon internalized aerobic bacteria for energy production A symbiotic relationship developed between the anaerobic host cells as they became increasingly dependent upon internalized aerobic bacteria for energy production  Mitochondria have their own DNA, known as mtDNA It is circular like prokaryotic DNA It is circular like prokaryotic DNA It duplicates by binary fission It duplicates by binary fission It has nothing in common with nuclear DNA It has nothing in common with nuclear DNA  mtDNA is passed to generations via maternal lineage ~ 100,000 mitochondria passed with ovum v. 50-100 passed with sperm; ~ 100,000 mitochondria passed with ovum v. 50-100 passed with sperm; Male mitochondria are eliminated from egg once fertilized Male mitochondria are eliminated from egg once fertilized  This consistent path of mtDNA, makes it prime candidate for molecular genealogy and anthropology

16. mtDNA Mutations/Dating Lineages  Mutation rate of mtDNA high b/c: Increased rate of mtDNA duplication Increased rate of mtDNA duplication Huge # of mitochondria in cells Huge # of mitochondria in cells  Called SNPs (single nucleotide polymorphisms) SNPs accumulate in mitochondria & passed via maternal lineage SNPs accumulate in mitochondria & passed via maternal lineage As lines of inheritance & populations diverge, separate paths develop own distinctive set of mutations As lines of inheritance & populations diverge, separate paths develop own distinctive set of mutations This mechanism used as a molecular clock to date fossils & compare to current mtDNA This mechanism used as a molecular clock to date fossils & compare to current mtDNA  MRCA (Most Recent Common Ancestor) mtDNA mutations used to determine MRCA; this helps determine when populations diverged & track migrations mtDNA mutations used to determine MRCA; this helps determine when populations diverged & track migrations

17. Who is “Eve?”  UC Berkeley research team (1987) Entire existing human population descendent from an African woman living ~150,000 yr ago Entire existing human population descendent from an African woman living ~150,000 yr ago Dubbed “mitochondrial Eve” – all existing mtDNA lineages in modern world branch from this “Eve” (called a halogroup) Dubbed “mitochondrial Eve” – all existing mtDNA lineages in modern world branch from this “Eve” (called a halogroup) An individual halogroup then tells which “daughter of Eve” a population descended from; halogroups divided into halotypes An individual halogroup then tells which “daughter of Eve” a population descended from; halogroups divided into halotypes  Some things about Eve: She is not the first human, She is not the first human, She had to have at least 1 female child that lived to reproduce, She had to have at least 1 female child that lived to reproduce, She is our MRCA She is our MRCA She is thought to have been a member of an original human population comprised of ~2000 interbreeding individuals She is thought to have been a member of an original human population comprised of ~2000 interbreeding individuals The mtDNA record does NOT reflect the existence of any of these other individualsThe mtDNA record does NOT reflect the existence of any of these other individuals Believed that all other lineages begat by other females in this population died out (became extinct)Believed that all other lineages begat by other females in this population died out (became extinct) Genetic evidence suggests a genetic bottleneck existed Genetic evidence suggests a genetic bottleneck existed

18. What the “bottleneck” led to…  This bottleneck may have been the result of some catastrophic event that so drastically reduced the numbers of the human population that this single woman’s DNA would have had a significant potential for expression in subsequent generations.  It is quite likely that to survive such a crisis and pass on her genetic material, “Eve” would have had to have been a member of a population isolated from the event or to have had traits that made her and her offspring able to endure the conditions.  D. Wallace, MD, Emory University researched mtDNA His team devised a family tree of all the female lineages in the world today His team devised a family tree of all the female lineages in the world today

19. 18 Daughters of Eve  Wallace’s tree has Eve at the base and 18 branches representing the 18 “daughters” who spread out from Eve’s origin  This split occurred ~ 144,000 YA Corresponds to when Y Chromosome tree projects branching took place Corresponds to when Y Chromosome tree projects branching took place (So, male lineage is traced via the Y chromosome, & female lineage is traced via mtDNA) (So, male lineage is traced via the Y chromosome, & female lineage is traced via mtDNA)  Regions in the world today have populations that have unique sets of mutations Wallace named these halotypes with a letter Wallace named these halotypes with a letter  Some of Wallace’s findings: Nearly all Native American mtDNA fits into halotypes A, B, C, D Nearly all Native American mtDNA fits into halotypes A, B, C, D Euorpean mtDNA appears to have descended from halotypes H –K & T-X Euorpean mtDNA appears to have descended from halotypes H –K & T-X These lineages suggest humans entered Europe ~39,000 to 51,000 YA, & this is supported by archeological evidenceThese lineages suggest humans entered Europe ~39,000 to 51,000 YA, & this is supported by archeological evidence

20. Reference  Mitochondrial DNA information obtained from the following site:  http://home.nc.rr.com/ambiient/site/mtdna. htm http://home.nc.rr.com/ambiient/site/mtdna. htm http://home.nc.rr.com/ambiient/site/mtdna. htm