Primer on Human Origins Evolution: Pattern & Process

Primer on Human Origins Theories of Evolution - The various theories of evolution and human origins. The Evidence - The material evidence related to evolution. The Future - Broader issues related to human origins, cosmology and the future of our little species. 1 Evolution: Pattern & Process “Evolution is the name we give both to patterns of change in the forms of life we observe, and to the process of natural selection that produces these patterns.” -- Philip Gingerich 2001 2 "light would be thrown on the origin of man and his history" 3 Modern Synthesis 4 Mutation Lepus tempermentalis Evolution Primer Rel. & Sci. 2010 5 Process of Natural Selection Population with variation Differential Reproduction Selective Filter Inheritance of useful traits Evolution Primer Rel. & Sci. 2010 6 Genetic Drift 25% 75% 6% 94% random walk simulation Evolution Primer Rel. & Sci. 2010 7 Fitness Landscape local vs Optimal adaptations Evolution Primer Rel. & Sci. 2010 8 9 Humans are Primates 10 Body Size Diversity Grey Mouse Lemur Microcebus murinus ~ 70 g Gorilla Gorilla gorilla > 100 kg 11 Overview of Primates Order Primates prosimians NW monkeys OW monkeys apes and humans 12 Distinguishing Characteristics of Primates 13 Grasping Hands and Feet 14 Nails not claws 15 Hind Limb Locomotion 16 Reduced Olfaction 17 Enhanced Vision 18 Unspecialized molars 19 High Parental Investment 20 Big Brains (encephalization) 21 Overview of Primates Order Primates prosimians Prosimii NW monkeys OW monkeys Anthropoidea apes and humans 22 Siamang Hominoids Gibbon Orangutan Gorilla Human Chimpanzee Bonobo 24 23 HOMINOID FEATURES • Distributed through Africa and SE Asia (except humans) • No tails • Dental formula 2123 • Y5 cusp pattern on the lower molars • Sexually dimorphic (except Hylobatidae) 25 Geological Timescale 26 Early Mammals Morganucodon Balanger’s tree-shrew 27 Cenezoic Age of Mammals 28 Primates Timeline 29 Living Great Apes Orangutan Gorilla Human Chimpanzee 6-8 Ma Molecular and anatomical The last common ancestor data support a sister group of chimps and humans lived relationship between humans sometime between 6-8 Ma. and chimpanzees. 30 Humans Chimpanzees 1 2 3 4 ? 5 6 7 Last Common Ancestor 31 Humans Chimpanzees 1 2 3 4 ? 5 6 7 Last Common Ancestor 32 33 ARTICLES Evolutionary Anthropology 7 statements are usually so complex that they cannot be directly compared and evaluated; in effect, the ability of the storyteller becomes as important Hominin as content in determining the plausi- bility of the whole.31 None of this is to suggest, of course, that trees and sce- narios should be eschewed: a lifetime Adaptations of cladograms would, after all, be te- dious indeed. But it does emphasize that when formulating phylogenetic hypotheses it is important to start with the simple before moving on to the complex. Any phylogenetic tree should be based on a cladogram, and any scenario on a tree; in this way, it is possible to see on what basis the more complex hypotheses have been formu- lated, even if they are not directly test- Scavenging/Hunting able themselves. Tool Use In the last quarter- century the language of cladistics has quite successfully penetrated paleoanthropology, although one cannot avoid the impression Megadonty that its underlying philosophy has been less thoroughly absorbed. In the last quarter-century the language of cladistics has quite successfully penetrated paleoanthropology, although one cannot avoid the im- Orrorin tugenensis (ca 6 Ma) pression that its underlying philoso- Bipedality Figure 3. Hominid phylogenetic tree based on the cladogram shown in Figure 2. Everyone phy has been less thoroughly ab- will be unhappy with at least some aspects of it, illustrating how much still remains to be sorbed. Still, the effect has been, at done inSahelanthropus the basic systematics of the hominid tchadensis fossil record. Modified (ca from7 Ma) Tattersall.1 least in34 some quarters, to refocus at- tention upon morphology. And al- tionary relationships postulated (i.e., and indeed the information contained though (myth to the contrary) cladis- ancestor-descendant, or separate de- in a single cladogram may be trans- tics in itself has little directly to do scent from the same ancestor). In pa- lated into a variety of trees.31 with the recognition of the basic units leontology, trees will also factor in Even more interesting and informa- of systematic analysis–rather, it is geological age. But while a tree is thus tive than the tree, but at the same time concerned with determining the rela- inherently more interesting than a cla- yet farther from testability, is the sce- tionships among taxa—its arrival in dogram, it is also less testable (be- nario, which adds to the mix every- paleoanthropology has been accom- cause it is impossible to prove or dis- thing you know about adaptation, panied by the realization that our per- prove a specific kind of relationship); ecology, and so forth. The resulting ceptions of the human biological past Piltdown Man HOAX “discovered” in 1912 in Sussex England’s Piltdown Quarry Large brain with hominoid (Orangutan mandible) Fit the expectation of a large brain matched with primitive teeth and jaw 35 Earliest Hominins 36 Bipedalism Austral. Homo Pan Pan Austral. Homo 37 AustralopithecusARTICLES Evolutionary Anthropology 7 statements are usually so complex that they cannot be directly compared and evaluated; in effect, the ability of the storyteller becomes as important as content in determining the plausi- bility of the whole.31 None of this is to suggest, of course, that trees and sce- narios should be eschewed: a lifetime of cladograms would, after all, be te- dious indeed. But it does emphasize that when formulating phylogenetic hypotheses it is important to start with the simple before moving on to the complex. Any phylogenetic tree should be based on a cladogram, and any scenario on a tree; in this way, it is possible to see on what basis the more complex hypotheses have been formu- lated, even if they are not directly test- Au. africanus able themselves. In the last quarter- century the language of cladistics has quite successfully penetrated paleoanthropology, although one cannot avoid the impression that its underlying Au. afarensis philosophy has been less thoroughly absorbed. In the last quarter-century the lan- Au. anamensis guage of cladistics has quite successfully penetrated paleoanthropology, although one cannot38 avoid the impression that its underlying philoso- Figure 3. Hominid phylogenetic tree based on the cladogram shown in Figure 2. Everyone phy has been less thoroughly ab- will be unhappy with at least some aspects of it, illustrating how much still remains to be sorbed. Still, the effect has been, at done in the basic systematics of the hominid fossil record. Modified from Tattersall.1 least in some quarters, to refocus at- tention upon morphology. And al- tionary relationships postulated (i.e., and indeed the information contained though (myth to the contrary) cladis- ancestor-descendant, or separate de- in a single cladogram may be trans- tics in itself has little directly to do scent from the same ancestor). In pa- lated into a variety of trees.31 with the recognition of the basic units leontology, trees will also factor in Even more interesting and informa- of systematic analysis–rather, it is geological age. But while a tree is thus tive than the tree, but at the same time concerned with determining the rela- inherently more interesting than a cla- yet farther from testability, is the sce- tionships among taxa—its arrival in dogram, it is also less testable (be- nario, which adds to the mix every- paleoanthropology has been accom- cause it is impossible to prove or dis- thing you know about adaptation, panied by the realization that our per- prove a specific kind of relationship); ecology, and so forth. The resulting ceptions of the human biological past ParanthropusARTICLES Evolutionary Anthropology 7 statements are usually so complex that they cannot be directly compared and evaluated; in effect, the ability of the storyteller becomes as important as content in determining the plausi- bility of the whole.31 None of this is to suggest, of course, that trees and sce- narios should be eschewed: a lifetime of cladograms would, after all, be te- dious indeed. But it does emphasize that when formulating phylogenetic hypotheses it is important to start with the simple before moving on to the complex. Any phylogenetic tree should be based on a cladogram, and any scenario on a tree; in this way, it is possible to see on what basis the more complex hypotheses have been formu- lated, even if they are not directly test- P. boisei able themselves. P. robustus In the last quarter- century the language of cladistics has quite successfully penetrated paleoanthropology, although one cannot avoid the impression that its underlying philosophy has been less thoroughly absorbed. P. aethiopicus In the last quarter-century the language of cladistics has quite successfully penetrated paleoanthropology, although one cannot39 avoid the impression that its underlying philoso- Figure 3. Hominid phylogenetic tree based on the cladogram shown in Figure 2. Everyone phy has been less thoroughly ab- will be unhappy with at least some aspects of it, illustrating how much still remains to be sorbed. Still, the effect has been, at done in the basic systematics of the hominid fossil record. Modified from Tattersall.1 least in some quarters, to refocus at- tention upon morphology. And al- tionary relationships postulated (i.e., and indeed the information contained though (myth to the contrary) cladis- ancestor-descendant, or separate de- in a single cladogram may be trans- tics in itself has little directly to do scent from the same ancestor). In pa- lated into a variety of trees.31 with the recognition of the basic units leontology, trees will also factor in Even more interesting and informa- of systematic analysis–rather, it is geological age.

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