PALEONTOLOGY

• How do we locate, recover, and date fossil remains? •What are the features

of the primate skeleton, and how can our knowledge of them help us identify fossil remains?

Stephen Jay Gould“…paleontologists have discovered several superb examples of intermediary forms and sequences, more than enough to convince any fair-minded skeptic about the reality of life's physical genealogy." (Natural History, May 1994)

23 Books: Ontogeny and Phylogeny, Ever Since Darwin, The Panda’s Thumb, The Mismeasure of Man, Hen’s Teeth and Horse’s Toes, The Flamingo’s Smile, Time’s Arrow, Time’s Cycle, An Urchin in the Storm, Wonderful Life, Bully for Brontosaurus, Eight Little Piggies, Dinosaur in a Haystack, Full House, Questioning the Millennium, Leonardo’s Mountain of Clams and the Diet of Worms, Rocks of Ages, The Lying Stones of Marrakech, The Structure of Evolutionary Theory, I Have Landed, The Hedgehog, The Fox, and the Magister’s Pox

US paleontologist, evolutionary biologist, historian of science (1941-2002)

THE FOSSIL RECORD: PRESERVATION

–Not a representative sample of all of the species that have lived on earth

–Some species and body parts preserve better than others

–TAPHONOMY = study of the processes that affect the remains of dead animals

THE FOSSIL RECORD: FINDING FOSSILS

* More likely to be found in areas with little vegetation and lots of erosion (i.e. lake bottoms)

* Due to issues regarding the preservation and discovery of fossils, the fossil record of early primates is “limited and spotty”

DATING CONCEPTS• PALEONTOLOGY = study of ancient

life through the fossil record

• Anthropology & Paleontology --interested in establishing a chronology for primate and human evolution

• Much dating depends on STRATIGRAPHY = study of the sequence of geographical layers

RELATIVE DATING

• Uses natural layers or strata to establish a relative chronology—material from this layer is older than the material from that layer

• Association with known fossils, biostratigraphy = most common method of fossil dating

ABSOLUTE DATING (p.202!)

• Produce dates in years, so differences in age can be quantified

• Radiometric techniques = based on known rates of radioactive decay in elements found in or around fossils

• Radiocarbon (Half-life of 14C is 5,730 yrs.), dates organic remains from 100s to 40,000 ya (half life = time needed for ½ amount of 14C to decay). Over 130 labs worldwide!

• Potassium Argon (K/A) dates volcanic rock from about 500,000 to billions ya

Lawrence Livermore National Laboratory

CAMS: The Center for Accelerator Mass Spectrometry

https://cams.llnl.gov/

ABSOLUTE DATING

• Electron Spin Resonance (ESR) = Measures # of electrons excited to higher energy levels by natural radiation & trapped at those levels, dates teeth & cave deposits from about 1000 ya to 1 mya

• Luminescence = Same as ESR, but trapped energy is released using heat or light, dates pottery, bricks, burned rock from about 5000 ya to 1 mya

Electron Spin Resonance (ESR) Facility: UCSC

• examines structure & properties of metal-containing inorganic complexes, peptides, proteins, enzymes, nanoparticles & membranes

• Bruker ELEXSYS 580 X-band spectrometer operates in either continuous-wave or pulsed mode, with variable temperature control

• Useful for limited sample sizes often encountered in biology

• Managed by Professor Glenn Millhauser (Dept. of Chemistry and Biochemistry)

•If Humanlike remains were found between two layers of volcanic rock, how could we date the remains?

• K/Ar (potassium/argon) dating

• Remains are younger than the volcanic deposit below and older than the one above

Hypothetical Stratigraphic Sequence

Absolute Dating Techniques

Technique Abbrev-iation

Materials Dated

Effective Time Range

Carbon 14 14C organic materials

up to 40,000 years

Potassium-Argon

K/A and 40K

volcanic rock

older than 500,000 years

Uranium Series

238U minerals between 1,000 and 1,000,000

Thermo-luminescence

TL rocks and minerals

between 5,000 and 1,000,000 years

Electron Spin Resonance

ESR rocks and minerals

between 1,000 and 1,000,000 years

Continents At End of the Mesozoic

Placement of the continents at the end of the Mesozoic and beginning of the Cenozoic, about 65 mya

Cenozoic Timescale

Taphonomy•What was found: accumulation of bones, including hominid bones, in South African caves

• Non-hominid bones, antlers, teeth: early tools used by bipedal “killer apes” to hunt and forage?

• What taphonomic research now shows: “killer apes” were prey not predator!

•Reconstruction shows: leopard eating remains of early hominid in tree above entrance to cave

Skeletons of:

• Modern Human

• Gorilla

• Domestic Cat

Skeletal Anatomy

Comparative Primate AnatomyDifferences in

stance:

Indri: Vertical clinging and leaping

Macaque: Generalized quadrupedalism

Gorilla: Semi-erect knuckle walking

Chimp: Knuckle-walking and tree climbing

Human: Fully erect bipedalism

Cranial Anatomy• Hominoid primates share same overall construction of the skull

• Proportions of the various bones of the skull, however, vary, as do the expression of various ridge-like features on surface of the bone

• What do you think are some of the reasons for these differences?

Sagittal crestFrontal

Brow ridge

Axial Skeleton (Trunk) of OW Primates

Changes in the anatomy of the trunk

Hominoid Comparative Anatomy

Changes in Human Skeleton

1. Skull more balanced on spine

2. Smaller neck muscles

3. Spine articulates under skull

4. Multiple curves of spine

5. Narrower rib cage

Changes in Human Skeleton (cont.)

6. Shorter wider pelvis

7. Proportionately longer legs

8. Upper leg angled inward so knees closer to midline

9. Big toe in line with other toes

10.Center of gravity in pelvic basin