Origin of Life Timeline and Early Earth Conditions

Origin of Life and the Universe

• The universe is approximately 13 billion years old, according to the Big Bang Theory and Doppler Shift.
• Earth is approximately 4.5 billion years old, formed through the cooling of the crust and solidification.

Earliest Record of Life

• The earliest recorded life form is from 3.5 billion years ago.
• The first human, Australopithecus, emerged around 0.005 billion years ago, with fossils discovered around 0.0000000002 billion years old.

Physical Conditions of Early Earth

• The temperature range on early Earth allowed for the existence of liquid water and non-brittle carbon compounds.
• The planet's size retained an atmosphere, which lacked oxygen, making it highly reductive.
• High-energy bombardment from the sun generated organics.

Evolution of Life

• Theories of life's origin include creationism, extraterrestrial origin/Panspermia, and spontaneous origin.
• Spontaneous origin theories involve abiotic synthesis, aggregation of proteins into abiotic membrane structures, and polymerization.

Biological Timescales

• Biological events are marked by geological timescales, with key events including mass extinctions and diversifications.
• The first fossil record of life dates back to 3.5 billion years ago, during the Precambrian era.
• The earliest eukaryote emerged around 1.5 billion years ago, through endosymbiosis.

Earth - The Early Years

• Late Precambrian saw the emergence of the first eukaryotic, multicellular life.
• The Cambrian explosion occurred between the Precambrian and Cambrian eras, with rapid adaptive radiation and diversification of marine life.
• The mid-Cambrian period saw the evolution of existing animal phyla.

Forces Behind Macroevolution

• Biological forces, such as natural selection, control allometric growth.
• Physical forces, such as plate tectonics, form and split supercontinents.

Study of Evolutionary History - Phylogeny

• Modern Darwinian theory involves adaptive radiation from a common ancestor.
• The concept of phylogeny is supported through studies of homology.
• Linnaeus' traditional classification systems are based on homology (parallel/divergent evolution) and analogy (convergent evolution).

The Kingdom System

• Campbell's classification scheme includes:
• Monera (pioneer organisms, 3.5 billion years old)
• Protista
• Plantae
• Fungi
• Animalia

Earth: The Middle Years

• The Permian extinction was the first major extinction at the end of the Paleozoic era, caused by tectonic plate collision.
• The Mesozoic era consisted of three periods: Triassic, Jurassic, and Cretaceous.
• The Cretaceous extinction was the second mass extinction.

The Evolution of Man

• Hominoids include placental mammals, apes (gibbons, orangutans, gorillas, chimpanzees), and humans.
• The divergence of Gorilla and Pan from Homo Sapiens occurred around 8 and 6 million years ago, respectively.
• Hominids include:
• Ardipithecus (earliest hominids, diverged 5 million years ago, bipedal)
• Australopithecus (most fossil specimens of early hominids)
• Homo (first humans, larger brain, evolving 2 million years ago)
• H.habilis (first tool users, "handy man", short person, long arms)
• H.rudolfensis (larger brain, coexisted with H.habilis)
• H.erectus (first true human, very large brain, NOT direct ancestor of modern humans)