Don Johanson Don Johanson

Hadar Knee Joint Australopithecus afarensis• Don Johanson, , 1973• Hadar, , Ethiopia• Age: 3-434 million yearsSignificance: The distalfemur and proximal tibiafragments articulate at anangle characteristic ofbipedal hominids, ratherthan quadrupedal apes.This confirmed that theHadar fossils werehominids.

Lucy(A.L. 288)Australopithecus afarensis• Don Johanson, , 1974• Hadar, , Ethiopia• Age: 3.2 million yearsSignificance: The most famous fossil of ourcentury, and the most complete specimenof any hominid this old. Three and a halffeet tall and fully bipedal with a chimp-sized brain, Lucy representsAustralopithecus afarenis, , the earliest well-described hominid species.

A.L. 333 “First Family”Australopithecus afarensis• Don Johanson, , 1975• Hadar, , Ethiopia• Age: 3.2 mSignificance: Hadar location 333 yielded the remains of nine adults and four juvenileses(including the child shown above and many of the Hadar jaws at the right). If itsdiscoverers are correct in their assumption that these individuals died together in acatastrophic event, the site offers a cross-section section of an afarensis population.

Meanwhile: Laetoli fossils & prints

Dating Hadar• Potassium-Argon• Fission Track• Paleomagnetism• BiostratigraphyLucyFirst Family

At first, Johanson shared Mary &Richard Leakey’s Interpretation:• Two types Lucy = “primitive” First family & Laetoli = Homo Evidence:• Small molars• Age of 1470• Homo is very old• Lucy not our ancestor(See Leakey’s s phylogeny in Origins)

Richard Leakey’s Phylogeny in Origins (1977)H. sapiens1 million years2 million years3 million yearsA. robustusLucy?A. africanusH. erectus14704 million yearsHomo sp.“First Family”Laetoli Footprints5 million years?

Why did Johanson Change?• Biostratigraphy?• Date of KBS tuff?• Allometry?If Lucy, First Family, & Laetoli are one, what are they?Not Homo!

How are hominid teeth different?• Canine size & shape• Canine dimporphism• Diastema• Canine and molar wear• Dental arcade shape• Premolar cusps

Hadar Teeth: Transitional• Canine size & shape• Canine dimporphism• Diastema• Canine and molar wear• Dental arcade shape• Premolar cusps

Don Johanson’s Phylogeny in Lucy (1981)H. sapiens1 million yearsA. robustusH. erectus2 million years1470A. africanus H. habilis3 million years4 million yearsA. afarensisLucy & “First Family”Laetoli Footprints5 million years?

Richard Leakey’s Phylogeny in Origins (1977)H. sapiens1 million years2 million years3 million yearsA. robustusLucy?A. africanusH. erectus14704 million yearsHomo sp.“First Family”Laetoli Footprints5 million years?

Don Johanson’s Phylogeny in Lucy (1981)H. sapiens1 million yearsA. robustusH. erectus2 million years1470A. africanus H. habilis3 million years4 million yearsA. afarensisLucy & “First Family”Laetoli Footprints5 million years?

Species: Australopithecus afarensis• Hadar + Laetoli fossils• Fully bipedal• Oldest hominid, 3-43mya• Smallest brain• Extreme dimorphism• Transitional dentalmorphology• Common ancestor of otherhominids

Don Johanson’s Phylogeny in Lucy (1981)H. sapiens1 million yearsA. robustusH. erectus2 million years1470A. africanus H. habilis3 million years4 million yearsA. afarensisLucy & “First Family”Laetoli Footprints5 million years?

Johanson’s reinterpretation ofAustralopithecines• Robusts are younger• Small molars ancestral (retained in Homo)• Large molars a derived Australopithecus trait Relativity of “ancestral” & “derived”• Graciles evolved into robusts

A Scientific Objection to Johanson Phylogeny• One species or two @ Hadar? Yves Coppens is among dissenters• “First family” interpretation circular?• Doubts linger

A. L. 444 - 2Australopithecusafarensis• Yoel Rak, , 1992• Hadar, , Ethiopia• Age: 3 million years• Cranial capacity: 500 ccSignificance: This large male is themost complete adult afarensis skullyet. It has fueled both sides of thedebate about the number of speciesat Hadar.

Next...Explaining Hominids