Unformatted text preview: Human Evolution
What makes us human? What's The Difference? Human and chimp DNA are ~ 98% similar. Gene duplications make up most of the differences. 30% of human and chimpanzee proteins are identical . The other proteins differ in only about 2 amino acids. The differences that make us human may be largely regulatory genes or DNA in the "dark matter" of the genome. Here is a striking difference 46 Human Chromosomes
(Haploid # = 23) 48 Chimpanzee Chromosomes
(Haploid # = 24) Gorillas and Orangutans also have 48 What is the reason for the difference? Fusion of ancestral 2A & 2B chromosomes to form human chromosome 2 Fusion of 2A & 2B without loss of a single gene What makes us human?
First Primate hand Second Upright posture/bipedalism Third Large complex brain Fourth Tool use, fire Evolved together Fifth Language Timeline of Hominid Evolution Primate Hands
Development of Opposable Thumb & Grasping Hand Power grip Precision grip Upright posture Frees hands for manipulation & carrying Brain Evolution Development Intelligence of the cerebral hemispheres Monkey Chimpanzee Human Look! What do you conclude from the graph showing Neanderthals had larger brains than modern humans? They were more intelligent. 2) There is an error in the data. 3) Brain size is not an index of intelligence. 4) The brain size of H. sapiens was larger when H. neanderthalensis was alive but has decreased since then. 30 5) I am confused
6 Tool Use in Non-humans Non-Primates Finch on Galapagos uses cactus needles Sea otters use rocks Elephants use sticks Egyptian Vultures use rocks Tool Use in Non-humans In Non-human Primates
use and make tools
Sticks Chimpanzees for termite fishing Leaves as sponges Sticks as clubs & spears Orangutans
Leaves as umbrellas Weave straw into rope swing Tool Use in Humans Austalopithicus Homo ? Some evidence habilis
tools & weapons Stone Homo erectus Hand axes Probably used fire Spears Clubs Digging sticks Language Chimpanzees use > 20 sounds for specific meaning ("words"). Trained to use American sign language & so the brain is adequate to handle simple speech. But.... ...their vocal apparatus seems to be inadequate Two major differences between human & chimp: 1) Shift in tongue position 2) Lengthening of Pharyngeal tract Australopithicus is Like a chimpanzee Neanderthals Probably were able to speak. Today = 10,000 Languages One origin FOXP2 gene and human speech
FOXP2 located on chromosome 7 found mutated in family with language dysfunction. Called the "language gene." FOXP2 is present in vocal and non-vocal animals & its loss is associated with motor skills and coordination including those of the mouth and face. In humans, its loss by mutation causes disturbance in language comprehension, grammar and syntax FOXP2 has rapidly evolved (2 amino acid substitutions since chimps.) Speculation that this difference is responsible for human speech. Neanderthals have the same FOXP2 gene structure as modern humans! What's The Difference? Not much . Four Interesting Problems How do the Neanderthals fit into the family tree? What are the migration patterns of humans? Why are there different races? When did we lose our body hair & develop clothing? New developments NEANDERTHALS DNA Analysis Complete mitochondrial DNA analysis of a Neanderthal shows 206 nucleotide differences between H.neanderthalis and H. sapiens split ~ 660,000 years ago
Cell 134 (3):416-426, 2008 Species Neanderthals
Lived in Europe & Middle East 200,000 23,000 yrs. (Gibraltar the last stronghold) Homo sapiens arrived in Europe ~40,000 yrs ago & lived together with Neanderthals ~20,000 years What did they look like? In 2007 a research team from the University of Leipzig announced they isolated a pigmentation gene (MC1R) suggesting that at least some Neanderthals had red hair, pale skin, and possibly freckles. The gene is unlike the red-haired gene of modern humans --evolved independently. Neanderthals
Used fire Buried dead Had musical instruments Tools & spear Why did they become extinct? Did humans and Neanderthals interbreed? No evidence that they did. But.....? ORIGINS & MIGRATIONS Origin of Homo sapiens Mitochondrial DNA "Eve" in mitochondria. Only mother gives mitochondria to young. mitochondrial DNA shows Africans to be the oldest group of H. sapiens. of H. sapiens 200,000 years ago in Africa. A very small population gave rise to modern humans Tracing Origin Homo sapiens Coming to America
Bering Strait Hypothesis: 2-3 migration waves walking across the land bridge Coming to America Bering Strait Hypothesis: 12,000 yrs ago--N. & S. Am. Indians 6,000 yrs ago--Navaho & Apache 4,000 yrs ago--Eskimo & Aleuts Clovis people--N. Mexico sites 11,500 years ago Into America Best Idea? Pacific route down coast of W. USA to S. Am. Explains Monte Verde, Chile site at 12,500 yrs. Ago \ RACES
Race concept: how many races? 335+ Why Are There Different "Races?"
A) Selective advantage to the different body forms in different environments. B) Sexual selection (mate choice) C) Genetic Drift D) Pleiotropy E) God made them that way
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5 Why Are There Different "Races?" Selective Few advantage to the different body forms in different environments?
good examples e.g. skin color But first, why are humans naked? THE NAKED APE Temperature regulation? The runner/hunter hypothesis. When did hominins lose their body hair? When did hominins begin to wear clothes? 54 54 A tale of three lice Lice are highly specialized blood sucking parasites that live on a single host species. Each of our ape relatives hosts one louse species, but humans host three types of lice. The head louse, Pediculus humanus capitus The body louse, Pediculus humanus corporis The pubic louse, Phthirus pubis 55 55 The body and head lice of chimps and humans are closely related. They are in the same genus. DNA analysis indicates they diverged 6 mya at the same time that the human and the chimp lines diverged. But the human pubic lice are so different that they are placed in a different genus. The head louse, Pediculus humanus capitus The pubic louse, Phthirus pubis The origin of pubic lice Use the phylogenetic tree on the next page to answer the following question: Given the phylogeny of select primates and their lice, what is the most likely origin of human pubic lice? 58 Phylogeny of selected primates & their lice Head lice Pubic lice 59 59 Given the phylogeny, what is the closest relative of human pubic lice? Chimp lice. B. Gorilla lice. C. Human head lice D. Rodent lice E. Monkey lice
C . 0%
E. The origin of pubic lice Surprise! Human pubic lice (Phthirus pubis) belong to the same genus as gorilla lice (Phthirus gorillae). comparisons show that human pubic lice and gorilla lice last shared a common ancestor 3-4 million years ago. But gorilla's and humans last shared a common 61 ancestor 7 mya. DNA 61 Hmmm... What were the Australopithecines and early gorillas up to? 62 The origin of pubic lice Hominins might have picked up lice from early gorillas by: Sleeping in nests recently used by early gorillas. Preying on early gorillas.
Lice are known to jump from prey to predator. Or .....??????????
63 63 The origin of body lice Human head and body lice are different morphotypes belonging to the same species. Human body lice live on clothing and move onto skin up to 5 times a day to feed. The head louse, Pediculus humanus capitus The body louse, Pediculus humanus corporis 64 64 A possible origin of body lice as distinct from head lice Human body lice arose because humans started to wear clothing.
A DNA comparison suggests the most recent common ancestor of human body lice lived less than 72,000 years ago. that when clothing started to be worn?
65 65 Is Back to the question of why are there different races?
Natural selection--specialization for different environments? Few examples. Skin color: variations in melanin pigment
Color is correlated with latitude
(north)-->Brown Black (south) Skin White Skin Color Correlated with Latitude North- less sunlight-->less vitamin D Less calcium More rickets. To prevent rickets Lose pigment ! South- more sunlight sunburn & hypervitamintosis D Keep pigment! European skin turned pale recently, Science April 20, 2007 -----long after Homo sapiens arrived in Europe. The mutation in gene SLC24A5 that causes pale skin in Europeans is only 6,000-12,000 yrs old Our ancestors were brown skin for thousands of years in Europe. What happened? Early immigrants were hunters/gatherers and had lots of vitamin D in their diet. Then when farming spread 6,000 yrs ago that changed. A Final Problem In 2004 a new species of fossil humans was discovered in Indonesia Homo floresiensis How does this fit into our phylogeny? Homo floresiensis Found in a cave on the island of Flores Homo floresiensis
3 feet tall Homo floresiensis Dated ~ 18,000 yrs ago. Phylogeny?
Homo floresiensis Homo erectus Homo habilis Homo sapiens ...
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