3.1 THE GREAT AGE OF THE EARTH DEBATE (p. 51)
- Archbishop James Ussher (1581-1656) and
a biblical chronology
- uniformitarianism: slow changes over immense stretches of time
Lord Kelvin (William Thompson 1824-1907)
Earth was no more than 20 million years old based on heat loss of
the Earth (Fig. 3.2)
- Did not take radioactivity into account
- relative dating
- geologic time
Unraveling Geologic Time from Paul Olsen's excellent WebPages for his dinosaur class
Geologic Time Scale from the UCMP
from the USGS
evolution is a time dependent process, special creation is not
- Principle of Fossil Succession: William Smith and Georges Cuvier
A relative dating activity
from the UCMP
a basic introduction by Pamela Gore
- radioactive decay [Box 3.1] is an independent clock
- the earth is 4.6 billion years old
- First possible life 3.8 billion years ago
- Stromatolites (cyanobacterial mats) 3.4 billion years ago (Fig. 3.1)1.
- Transition to eucaryotic life began at least 2.1 billion years
- Diverse and unique animals dominated the oceans from 575
- 535 mya
Burgess Shale (Fig. 3.20)
- Chordates emerged during early Cambrian(515 mya); Jawed fish by 440 mya (Fig 3.21)
- Oldest fossils of tetrapods date to 370 mya (Figs. 3.24-3.25)
- Oldest amniotes date to 340 mya
- Teleost fish (most ray-finned fish): Triassic, 240 Ma
- Birds: Jurassic, 150 Ma
- Flowering plants: early Cretaceous,120 million years ago
Evolution of Mammals
- Pelycosaur synapsids emerged around 300 mya (Fig 3.26)
- First mammals emerged 150 mya
- Mammals diversified after dinosaurs went extinct (~65 mya)
- Whales, bats, and primates all emerged around 50 mya
- Oldest hominins ~7 mya
EVIDENCE OF CHANGE THROUGH TIME
4.1 Tree Thinking p. 95
- Phylogenies are hypotheses that are constructed using
shared, derived characters.
- These characters can be morphological or genetic.
- Reading a Tree
- species are related by descent from a common ancestor.
- Evolutionary trees describe histories of descent with
- Darwin's hypothetical tree (Figure to right), showing a phylogeny
with tips, branches, and nodes, is the only figure in The Origin
- Cladograms show the
relationships of taxa
- Journey into the world of
phylogenetic systematics from the UCMP
4.4 Fossils, Phylogeny, and
the Timing of Evolution p. 106
- Incorporating fossils into phylogenies makes it possible to discover
things that we would not know if we studied only the taxa alive today
- The Law of Succession
- Lyell saw a 'law of succession' with mammals being replaced by their
own kind on each continent
- Darwin noted the
similarities between the contemporary pygmy armadillo (Zaedyus pichyi) and the fossil glyptodont of Argentina.
Owen confirmed a pattern first recognized by William Clift when Owen
identified the extinct Australian mammal
as a marsupial
similar to the wombats that live in Australia today
From Fins to Limbs: Homology through Time p.
- The colonization of land marks an important evolutionary transition now documented in the
Tiktaalik (Figs. 4.2, 4.201 4.22)
Evolution as Tinkering p. 114
- Adaptations do not appear magically in the fossil record
- existing components can be modified and co-opted for new functions
- selection can lead to new characteristics by changing functions of
preexisting traits, genes, etc.
- preadaptations, exaptiion
- The mammalian middle ear (Figs. 4.25-27)
Feathered Dinosaurs Take Flight p. 118
are not unique to birds, and they did not evolve for flight.
- The dinosaur-bird transition (Fig. 4.29)
(Fig 4.28), a bird with modern feathers and a dinosaur-like
- Sinosauropteryx prima, a dinosaur with bristly structures
on its neck, back, flanks, and tail that many paleontologists believe
are down-like feather
zoui, a dinosaur with elongated feathers on its arms and tail.
huxleyi, (Fig. 3.8)
- Microraptor gui,
a dromaeosaur with flight feathers on all four limbs--that is, a
Tiktaalik in the
Museum, Chicago. Image from
A New Ape (Chapter 17)
- Humans have a grand history
- a history being discovered in depth as more and more fossil
hominids are unearthed.
- Darwin proposed that humans most closely related to
- Fossil record should document transition
to to unique human traits
- Larger brain size
- Smaller canine teeth
- Phylogeny reveals transitions (Fig. 17.6)
- Transition to bipedality (Fig. 17.7)
- Appears to have evolved before larger
- Position of foramen magnum
- Weight bearing stance
- Short, stiff toes
Ardipithecus (5.5-4.4 Ma), adapted to walking and arboreal life
Ardipithecus Zanclean skull.
by T M Keesey
- Hominins became better adapted to walking upright over time
- Tracks made by Australopithecus afarensis
(3.6 mya) and Homo 1.5 Ma (Fig.
- Homo erectus (Fig. 17.7)
Freeman and Herron Chapter 20
DOWNLOAD an Adobe Acrobat version of the
species distributed through time.
- Figure 20.1 Phylogeny of the apes
- This evolutionary tree shows the relationships among the Old World monkeys, represented by a rhesus monkey, and the apes and humans. Among
the apes, the gibbons branch off first, followed by the orangutan. The evolutionary relationships among the gorilla, the two chimpanzees, and
humans (triangle with question mark) were long the subject of considerable dispute
- Phylogeny based on anatomy
- Figure 20.2 Sarich and Wilson's phylogeny of the apes.
- Immunological distance (antibody response), showing humans and African apes diverged about 5 Ma.
- Figure 20.3 Possible phylogenies of humans and the African great apes
- The figure shows four possible resolutions
of the evolutionary relationships among humans and the African great apes.
All assume that the two species of chimpanzee are closest relatives. The
true tree could have (a) chimpanzees and humans as closest relatives, (b)
gorillas and chimpanzees as closest relatives, (c) gorillas and humans as
closest relatives, or (d) a genuine simultaneous three-way split (trichotomy).
- Figure 20.4 Phylogeny of mitochondrial cytochrome oxidase II alleles in humans
and the African great apes. Ruvolo and
colleagues estimated this tree using the maximum parsimony method.
- Figure 20.6 Divergence times for the apes
- Stauffer and colleagues estimated the dates
of the common ancestors on this phylogeny by combining data from dozens of
proteins used as molecular clocks. The heavy bars show +/- 1 standard error
around the time estimates; the lighter bars show 95% confidence intervals.
- Figure 20.7 Human chromosome 2 and its homologues in chimpanzees and gorillas
- The banding patterns on stained chromosomes
reveal that human chromosome 2 is derived from the fusion of two chromosomes
that remain separate in the other great apes.
Telling apes from humans Panda's Thumb
are always very definite that there are absolutely,
transitional fossils between apes and humans."
are some photos of fossil skulls, all to the same scale. Some are of humans,
some of apes. Care to identify which are which?
- Figure 20.9
- This 6-7 million-year-old skull, found by a
member of a team led by Michel Brunet, may represent a close relative of our
common ancestor with the chimpanzees. From Wood (2002).
- Ardipithecus ramidus
New York Times article
- Figure 20.10.
Gracile australopithecines, Kenyanthropus, and Ardipithecus
Ardipithecus (5.5-4.4 Ma), with species
Ar. kadabba and
Australopithecus (4-2 Ma), with species
Au. bahrelghazali, and
Kenyanthropus (3-2.7 Ma), with species
Figure 20.11 Footprints of a pair of
- These 3.6-million-year-old footprints from
Laetoli, Tanzania were made by a pair of
individuals who walked side-by-side through fresh ash from a volcanic
- Figure 20.12
Paranthropus (3�1.2 Ma), with species
P. boisei, and
- Figure 20.13: Early humans
- Figure 20.14: Recent humans
H. neanderthalensis, H. sapiens
- Figure 20.15 Summary of fossil evidence on the recent ancestry of humans
- The vertical axis gives approximate time
ranges for the species we have mentioned. Horizontally, the hominin species
are grouped roughly by morphological similarity. Chimpanzees are the
20.15 from Darwiniana:
- Figure 20.16: Cladogram and phylogeny of
sapiens and its recent ancestors and extinct relatives
- A cladogram of three extant
hominins (the gorilla, the common chimpanzee, and the modern human), and
several extinct hominins known only from fossils.
- A hypothesis about the ancestor-descendant
relationships implied by the cladogram in (a). The heavy green vertical bars
indicate the known range of times over which each species existed, whereas
the heavy green dashes represent the suspected range of times over which
each species existed.
20.17 Evidence of a hominin radiation
- Paranthropus boisei
(specimen KNM-ER 406, left) and Homo ergaster (specimen KNM-ER 3733) both lived in what is now Koobi Fora, Kenya, about 1.7 million years ago. From
Johanson, Edgar, and Brill (1996).
20.18 Hypotheses concerning the transition from Homo ergaster/erectus
to Homo sapiens
- The white portions of the phylogenies
represent various archaic forms of Homo, including H. ergaster, H. erectus, H. heidelbergensis, and H. neanderthalensis.
The colored portions represent modern H. sapiens. The small blue
arrows represent gene flow. Note that specimens identified as H.
heidelbergensis have been found in Europe and Africa, and specimens
identified as H. neanderthalensis have been found in Europe and the Middle East.
- (a) The African replacement model.
According to this model, modern H. sapiens evolved in Africa and
then migrated to Europe and Asia. H. sapiens
replaced the local forms without hybridization. No genes from these
earlier forms persist in modern human populations.
- (b) The hybridization and assimilation
model. According to this model, modern H. sapiens evolved in Africa and then migrated to Europe and
Asia. H. sapiens largely replaced the local populations, but there
was hybridization between the newcomers and the established residents. As
a result, some genes from the archaic local populations were assimilated
and persist in modern human populations.
- (c) The multiregional evolution model.
According to this model, H. sapiens evolved concurrently in Europe,
Africa, and Asia, with sufficient gene flow
among populations to maintain their continuity as a single species. Gene
pools of all present-day human populations are derived from a mixture of
distant and local archaic populations.
- (d) The candelabra model: H. sapiens
evolved independently in Europe, Africa, and Asia, without gene flow
among populations. All genes in present-day European and Asian populations
are derived from local archaic populations.
- Figure 20.21 Phylogenetic predictions of the African replacement model versus
the multiregional evolution model. (a) The
African replacement model predicts that all modern humans will be more closely
related to each other than any is to any archaic species and that, among the
archaic species, those from Africa will be the most closely
related to modern humans. (b) In contrast, the multiregional evolution model
predicts that the archaic and modern humans in each region will be each
other's closest relatives. From Lieberman (1995).
- Figure 20.22 Phylogeny of Neandertals and modern humans. This cartoon summarizes evidence from analyses of mitochondrial DNA sequences from several hundred modern humans and three Neandertals. The
split between Neandertals versus humans predates the diversification within
each lineage by a substantial margin. This suggests that modern humans are a
distinct lineage from Neandertals and replaced them without hybridization.
After Ingman et al. (2000),
Krings et al. (2000), Ovchinnikov et al.
(2000), and Hoffreiter et al. (2001).
- Table 20.1 Genetic distances between humans,
chimpanzees, and gorillas
- Figure 20.8 Differences in gene expression patterns in different tissues of
humans, chimps, and rhesus macaques
- These unrooted trees represent the
divergence in overall patterns of gene expression in humans versus
chimpanzees versus rhesus macaques. The numbers on the human branches
represent the ratio of the human divergence versus the chimp divergence. In
blood and liver, humans have diverged from the common pattern about as much
as chimps have. In brain, however, humans have diverged considerably more.
- Figure 20.32 Brain size versus body size in a variety of hominins and great
apes. Data points represent species averages,
with best-fit lines. In all three groups, species with larger brains have
larger bodies. Australopithecines have larger brains for their size than
extant great apes. Homo species have larger brains for their size, as
well as a dramatically different relationship between brain size and body
size. The extant great apes are the bonobo, common chimpanzee, orangutan, and
gorilla; the australopithecines are A. afarensis, A. africanus, P. boisei, and P. robustus; the Homo species are H.
habilis, H. ergaster/erectus, and H. sapiens. The
data are from Tobias (1987) and Pilbeam and Gould (1974). See also McHenry
(1994). After Pilbeam and Gould (1974).
- Human and ape ontogeny.
Box 4.5 The Tree of Life -- or Perhaps the Web of Life
Horizontal Gene Transfer
- Image from
Wikipedia by Barth Smets: tree of life showing vertical and
horizontal gene transfers.