Human Evolution
Human Evolution I. What are humans related to?
Human Evolution I. What are humans related to? - Morphologically similar to apes
Human Evolution I. What are humans related to? - Morphologically similar to apes - hands, binocular vision (Primates) No tail
Human Evolution I. What are humans related to? Apes
Human Evolution I. What are humans related to? Apes II. How do we differ?
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect)
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect) - Behaviorally (intelligence and learning)
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect) - Behaviorally (intelligence and learning) - Morphologically, humans have: - larger head/body ratio
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect) - Behaviorally (intelligence and learning) - Morphologically, humans have: - larger head/body ratio - smaller jaw/head ratio
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect) - Behaviorally (intelligence and learning) - Morphologically, humans have: - larger head/body ratio - smaller jaw/head ratio - shorter arms/body ratio
Human Evolution I. What are humans related to? Apes II. How do we differ? - Behaviorally (walk erect) - Behaviorally (intelligence and learning) - Morphologically, humans have: - larger head/body ratio - smaller jaw/head ratio - shorter arms/body ratio - less hair
Human Evolution I. What are humans related to? Apes II. How do we differ? - Morphologically Human Chimp Gorilla Orangutan Gibbon
Human Evolution I. What are humans related to? Apes II. How do we differ? - Genetically: Big Surprize! Human Chimp Gorilla Orangutan Gibbon
Human Evolution I. What are humans related to? Apes II. How do we differ? - Genetically: Big Surprize! Human Chimp Gorilla Orangutan Gibbon < 1% difference in gene sequence
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? Can this 1% difference account for the dramatic behavioral and morphological differences we see? Yes, some genes have big effects. These are regulatory genes, acting during development. They influence the expression of lots of other genes…
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? Can this 1% difference account for the dramatic behavioral and morphological differences we see? Yes, some genes have big effects. These are regulatory genes, acting during development. They influence the expression of lots of other genes… - Can we test this hypothesis? Do the differences correlate with developmental effects?
Yes. All differences correlate with developmental differences between juvenile primates and adults… Juveniles Adults Larger Head/body ratio smaller Smaller jaw/head ratio larger Shorter limb/body ratio longer Less hair more hair Better learning poorer learning
Yes. All differences correlate with developmental differences between juvenile primates and adults… Juveniles Adults Larger Head/body ratio smaller Smaller jaw/head ratio larger Shorter limb/body ratio longer Less hair more hair Better learning poorer learning Human-like Ape-like
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? Can this 1% difference account for the dramatic behavioral and morphological differences we see? Yes, if the small change is in developmental genes, they can have BIG effects…humans might be a type of ape that didn’t grow up… The ways we differ supports this hypothesis…
Yes, if the small change is in developmental genes, they can have BIG effects…humans might be a type of ape that didn’t grow up… Small changes in development, especially if they occur early in development, can result in big effects. Human Chimp Primate developmental trajectory
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? IV. Are there common ancestors?
Molecular clock analyses
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? IV. Are there common ancestors? Yes. Just where evolution predicts they should be (After other monkeys and apes, before humans and existing apes).
Science, Nov 19, 2004 12-13 mya – oldest ape Pierolapithecus catalaunicus 12-13 mya – oldest ape
V. Are there common ancestors? - Fossil and genetic analysis independently predicted a common ancestor between humans and chimps lived 5-8 million years ago. Chimpanzee Human Homo sapiens
V. Are there common ancestors? - Fossil and genetic analysis independently predicted a common ancestor between humans and chimps lived 5-8 million years ago. Chimpanzee Human Homo sapiens Sahelanthropus tchadensis – discovered in Chad in 2001. Dates to 6-7 mya. Only a skull. Is it on the human line? Is it bipedal? Probably not (foramen magnum). Primitive traits, as a common ancestor might have.
Human Evolution I. What are humans related to? Apes II. How do we differ? III. Resolution? IV. Are there common ancestors? V. Are there intermediate links to modern humans?
V. Are there intermediate links to modern humans? - yes, and in a nearly continuous sequence…. Chimpanzee Australopithecus afarensis Australopithecus africanus Homo habilis Human Homo sapiens Homo erectus
V. Are there intermediate links to modern humans? - with a divergence of two types of hominids around 2 mya
V. Are there intermediate links to modern humans? - with a divergence of two types of hominids around 2 mya
V. Are there intermediate links to modern humans? - with a divergence of two types of hominids around 2 mya “slender” species
V. Are there intermediate links to modern humans? - with a divergence of two types of hominids around 2 mya “slender” species “robust” species
V. Are there intermediate links to modern humans? - with a divergence of two types of hominids around 2 mya Primitive species, with their bipedality disputed. Are they on the human line? The chimp line? Ancestral to both? Can’t tell – they are so INTERMEDIATE….
Morphological cladogram