Evolutionary Genetics

The Geological Time Scale

Geological time scaled to a cross-country tour of Canada.

The universe came into existence about 14 billion years ago, through an explosion known as the "big bang".

Our galaxy formed from clouds of dust and gas about 10 billion years ago.

We begin our cross-country tour in St. John's Newfoundland, the eastern-most city in Canada (6240 km to Vancouver), which we will make correspond in distance to the formation of the earth around 4.6 billion years ago (BYA).

Every kilometer in our tour will therefore cover 0.737 million years (MY).

Saint John's, Newfoundland: [6240 km] ~ 4.6 BYA, Beginning of Hadean Eon

The formation of the earth and solar system.

Earth was molten and extremely hot at first, slowly cooling and forming land and water masses.

Initially, little atmospheric oxygen was present.

Saint John, New Brunswick: [5211 km] ~3.8 BYA, Eon Hadean.

Oldest surviving rocks on earth.

Quebec City, Quebec: [4643 km] ~3.5 BYA, Near beginning of Archean Eon.

First evidence of life

Bacteria-like microfossils and layered fossil mats, known as stromatolites, provide the first evidence of life on earth.

Dryden, Ontario: [2628 km] ~2 BYA, Near beginning of Proterozoic Eon.

First eukaryotes (single-celled algae). The symbiotic origin of mitochondria and chloroplasts followed by 1.4 BYA.

Calgary, Alberta: [962 km] ~800 MYA, Eon Proterozoic.

Trace evidence, including burrows, of first metazoans (= multicellular animals with differentiated tissues)

More definite fossil evidence of metazoans comes from the late Proterozoic. In particular, the Ediacaran fauna from Australia consists of a number of soft-bodied, aquatic animals resembling jellyfish and worms.

Yoho National Park, British Columbia: [740 km] ~543 MYA, Beginning of Paleozoic Era (Cambrian Period).

Diversification of metazoans. Increase in oxygen levels, approaching modern levels.

Cambrian explosion: "Almost all the modern phyla and classes of skeletonized marine animals, as well as many groups that may represent extinct phyla and classes, suddenly appear in the fossil record...within about 30, perhaps only 5 to 10, million years."

Futuyma (1998) p. 172

Most of the fundamental body plans (bauplane) had evolved by the end of the Cambrian Period. The most spectacular collection of Cambrian fossils comes from the Burgess shale, right here in Yoho National Park!

Important events in the Paleozoic Era:

1^st shells in the Cambrian Period (543-500 MYA)
1^st fish in the Ordovician Period (500-439 MYA)
Mass extinction
1^st land plants in the Silurian Period (439-409 MYA)
1^st amphibians and true insects in the Devonian Period (409-354 MYA)
Mass extinction
1^st reptiles in the Carboniferous Period (354-290 MYA)
Diversification of the reptiles in the Permian Period (290-251 MYA)
Mass extinction (P/Tr boundary)

Kamloops, British Columbia: [348 km] ~251 MYA, Beginning of Mesozoic Era (Triassic Period).

"Age of Reptiles". Break-up of Pangaea (single large landmass including all present-day continents). Warm climate.

Important events in the Mesozoic Era:

1^st dinosaurs and mammals in the Triassic Period (251-206 MYA)
Mass extinction
1^st birds and angiosperms in the Jurassic Period (206-144 MYA)
Diversification of mammals, birds, and angiosperms in the Cretaceous Period (144-65 MYA)
Mass extinction (K/T boundary)

Chilliwack, British Columbia: [90 km] ~65 MYA, Beginning of Cenozoic Era (Tertiary Period).

"Age of Mammals". Break-up of Gondwanaland (landmass containing southern continents and India). Cooling of climate.

Important events in the Cenozoic Era:

Radiation of mammals, birds, snakes, angiosperms, pollinating insects, and teleost fish into their modern orders in the Tertiary Period (65-1.8 MYA)
1^st Homo fossils in Quaternary Period (1.8 MYA-Present)

Broadway and Vine (Kitsilano), Vancouver: [6.8 km] ~5 MYA, Era Cenozoic (Tertiary Period).

Divergence of hominid and chimpanzee lineages.

UBC Golf Course, Vancouver: [2.4 km] ~1.8 MYA, Era Cenozoic (Quaternary Period).

Beginning of Pleistocene epoch. Massive fluctuations in temperature (~100,000 year period), leading to major glacial advances and retreats.

Forest Sciences building, UBC, Vancouver: [24 m] ~18,000 YA, Era Cenozoic (Quaternary Period).

Last ice age at its maximum.

Room 1005 door, Forest Sciences, UBC, Vancouver: [16 m] ~12,000 YA, Era Cenozoic (Quaternary Period).

Development of agriculture.

The span of my hand: [19 cm] 139 YA, Era Cenozoic (Quaternary Period).

The Origin of Species is published.

MYA EON ERA PERIOD EPOCH MAJOR EVENTS

0.01 P
H
A
N
E
R
O
Z
O
I
C C
E
N
O
Z
O
I
C Quarternary Recent Development of agriculture and human civilization

1.8 Pleistocene Appearance and world-wide spread of the genus Homo. Repeated glaciations. Extinctions of large mammals and birds.

5.2 Tertiary Pliocene Continued diversification of modern birds, placental mammals, snakes, teleost fish, pollinating insects, grasses and angiosperms.

24 Miocene

34 Oligocene

56 Eocene

65 Paleocene

144 M
E
S
O
Z
O
I
C Cretaceous Diversification of flowering plants, birds and mammals.

206 Jurassic 1^st birds and angiosperms. Dinosaurs abundant.

251 Triassic 1^st dinosaurs and mammals. Gymnosperms become abundant. Continents moving apart.

290 P
A
L
E
O
Z
O
I
C Permian Diversification of reptiles, including mammal-like species. Land masses form single continent, Pangea.

354 Carboniferous 1^st reptiles and winged insects. Warm humid conditions result in huge forests of primitive plants, which formed extensive coal deposits.

409 Devonian 1^st amphibians and true insects. Atmospheric oxygen at present levels or higher. Continents moving toward one another.

439 Silurian 1^st land plants. Atmospheric oxygen about 20 percent.

500 Ordovician 1^st fish.

543 Cambrian 1^st shelled organisms. Trilobites abundant. Probably all metazoan phyla present, including arthropods and early chordates. Atmospheric oxygen reaches about 2%.

2,500 PROTEROZOIC Abundant prokaryotic life. Eukaryotes may have appeared by 2,000 million years ago. Atmospheric oxygen about 0.2%.

3,600 ARCHEAN Oldest known rocks and prokaryotes.

4,600 HADEAN Earth forms. No geological record.

From Futuyma (1998), p. 130, using dates of Jablonski et al. (1996).

SOURCES:

Futuyma (1998) Evolutionary Biology. Sinauer Associates, MA.

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MYA	EON	ERA	PERIOD	EPOCH	MAJOR EVENTS
0.01	P H A N E R O Z O I C	C E N O Z O I C	Quarternary	Recent	Development of agriculture and human civilization
1.8			Quarternary	Pleistocene	Appearance and world-wide spread of the genus Homo. Repeated glaciations. Extinctions of large mammals and birds.
5.2			Tertiary	Pliocene	Continued diversification of modern birds, placental mammals, snakes, teleost fish, pollinating insects, grasses and angiosperms.
24				Miocene
34				Oligocene
56				Eocene
65				Paleocene
144		M E S O Z O I C	Cretaceous		Diversification of flowering plants, birds and mammals.
206			Jurassic		1^st birds and angiosperms. Dinosaurs abundant.
251			Triassic		1^st dinosaurs and mammals. Gymnosperms become abundant. Continents moving apart.
290		P A L E O Z O I C	Permian		Diversification of reptiles, including mammal-like species. Land masses form single continent, Pangea.
354			Carboniferous		1^st reptiles and winged insects. Warm humid conditions result in huge forests of primitive plants, which formed extensive coal deposits.
409			Devonian		1^st amphibians and true insects. Atmospheric oxygen at present levels or higher. Continents moving toward one another.
439			Silurian		1^st land plants. Atmospheric oxygen about 20 percent.
500			Ordovician		1^st fish.
543			Cambrian		1^st shelled organisms. Trilobites abundant. Probably all metazoan phyla present, including arthropods and early chordates. Atmospheric oxygen reaches about 2%.
2,500	PROTEROZOIC				Abundant prokaryotic life. Eukaryotes may have appeared by 2,000 million years ago. Atmospheric oxygen about 0.2%.
3,600	ARCHEAN				Oldest known rocks and prokaryotes.
4,600	HADEAN				Earth forms. No geological record.