Transcript Lecture: Fossils and Comparative Anatomy

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, US paleontologist, evolutionary biologist,
and the Magister’s Pox
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)
Hypothetical Stratigraphic Sequence
•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
Absolute Dating Techniques
Technique
Abbreviation
Materials
Dated
Effective Time Range
Carbon 14
14C
organic
materials
up to 40,000 years
PotassiumArgon
K/A and
40K
volcanic
rock
older than 500,000 years
Uranium Series
238U
minerals
between 1,000 and
1,000,000
Thermoluminescence
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
Skeletal Anatomy
Skeletons of:
• Modern Human
• Gorilla
• Domestic Cat
Comparative Primate Anatomy
Differences in stance:
Indri: Vertical clinging
and leaping
Macaque: Generalized
quadrupedalism
Gorilla: Semi-erect
knuckle walking
Chimp: Knucklewalking 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?
Brow ridge
Frontal
Sagittal crest
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