How and when the life began?

• The age of Earth was estimated as about 4.6 billion years old based on the age of meteorites by Clair C. Patterson (1922–1995) - using Uranium-Lead

dating on fragments of the Canyon Diablo meteorite and published in 1956*.

• Chemical evolution (or Abiogenesis) is the first process by which rocks, water and gases chemically combined to form essential molecules (monomers) and eventually result in the formation of nucleic acids (e.g. RNA) and living cells.

• During the early time, Earth atmosphere contained simple compounds composed principally of hydrogen, carbon, oxygen and nitrogen including water vapor, methane, hydrogen and ammonia – Primordial Soup conditions.

*http://www.nationmaster.com/encyclopedia/Age-of-the-earth

Concept Map

Primordial

Soup

Clay

SurfaceHydro-

thermal Vent

Multi-cellular

organisms

e.g. sponges

Single-celled

organisms

Oxygen limited

Abiogenesis

Modified from Paul Anderson

Stanley Miller (1930-2007) Harold Urey (1893-1981)

Nobel Prize in Chemistry in 1934

In 1953, two

pioneers tested

the abiogenesis

hypothesis

Miller-Urey Experiment

• In 1953, Stanley Miller and Harold Urey carried out this important experiment at Chicago University.

• They mixed H2O, CH4, H2 and NH3

in a large flask with electrical sparks generated by 2 electrodes.

• After few days, the liquid became cloudy and turned to dark brown color.

• Chemical analysis revealed that the brownish liquid contained a large amount of amino acids (25), carbohydrates, fatty acids etc.

Step 2

CH2O + HCN +NH3 → NH2·CH2·CN +H2O

NH2·CH2·CN + 2H2O → NH3 +NH2·CH2·COOH (glycine)

Jeffrey Bada

Step 1

CO2 → CO + [O] (atomic oxygen)

CH4 + 2[O] → CH2O + H2O

CO + NH3 → HCN + H2O

CH4 + NH3 → HCN + 3H2 (BMA Process)

Further Experiments

• After Miller-Urey experiment in 1953, many scientists conducted modified experiments to more closely match what scientist now think were primitive Earth conditions.

• For example, they used nitrogen and carbon dioxide instead of ammonia and methane, and adding common minerals to the initial mixture liquid.

• These experiments reveal how easy it is to make all sorts of organic molecules, including lipids and bases, as well as complex substances such as long protein chains and nucleic acids.

Primordial

Soup

Clay

SurfaceHydro-

thermal Vent

Multi-cellular

organisms

e.g. sponges

Single-celled

organisms

Oxygen limited

Abiogenesis

Modified from Paul Anderson

Black Smokers – discovered in 1979

• Black Smokers– Deep-ocean floor

– Vents of mineral rich hot water

– Diverse ecosystem• Most primitive bacteria

• Hydrothermal zones– Site of life’s origin?

• Protected

• Ideal chemical environment

The First Cell – before stromatolites ?

Modern stromatolites in Shark Bay, Western Australia 3.2-3.5 billion years old

The Window of Opportunity

• Rapid chemical processes

• Stromatolites– 3.2-3.5 billion years old

• Recent discoveries

– J. William Schopf, University of California

• Evidence of life 3.5 billion years ago*(a paper in Science appeared in 1993)

– Gérard et al. (2009) have recently documented the presence of modern bacteria in drill-core samples of rocks that are 2.7 billion years old.

*http://sandwalk.blogspot.hk/2009/09/did-life-arise-35-billion-years-ago.html

Primordial

Soup

Clay

SurfaceHydro-

thermal Vent

Multi-cellular

organisms

e.g. sponges

Single-celled

organisms

Oxygen limited

Abiogenesis

Modifie

d fro

m P

aul A

nders

on

?

?

?

?

RNA World

RNA Enzymes & The First Cell

• Early life was simpler– RNA catalyzed reactions

– Created proteins

– Proteins led to DNA

• First cell

– No competition

– Multiplied rapidly

Why we think RNA first?• Translation depends on RNA:

- mRNA supplies the information for protein synthesis

- active ingredient of the ribosome is rRNA

- tRNA also essential for translation

• In Miller’s experiments, ribose (component of RNA) was created and deoxy-ribose (in DNA) was harder to produce. Deoxy-ribose tends to decompose better than ribose.

• RNA is simpler than DNA.

• It exists in viruses (and no DNA)

RNA first?

Primordial

Soup

Clay

SurfaceHydro-

thermal Vent

Multi-cellular

organisms

e.g. sponges

Single-celled

organisms

Oxygen limited

Abiogenesis

Modifie

d fro

m P

aul A

nders

on

?

?

?

?

RNA World

Organic Matter

from Space

Organic Matters from Space

Nature, 430, 985 (2004)

Nature, 479, 80 (2011)

BBC First Life – David Attenborough on Youtube

http://www.youtube.com/watch?v=NZJ8Zk2VvN4

(more complete but not HD)

With English sub-title:

http://www.youtube.com/watch?v=1yiJv6KkMXI&feature=channel&list=UL

http://www.youtube.com/watch?v=8N8hjyVuRIw&feature=channel&list=UL

http://www.youtube.com/watch?v=6vg4vSYRyNU&list=UUaltokhFFrhNInAKvCV4knw&index=12&feature=plcp

BBC Life on Earth: The Infinite Variety – Parts 1-6 on Youtube:

Part 1: http://www.youtube.com/watch?v=yDdaStk5SEM

Part 2: http://www.youtube.com/watch?v=HStl89NXdHQ

Part 3: http://www.youtube.com/watch?v=k_TdbzIje7s&feature=channel&list=UL

Part 4: http://www.youtube.com/watch?v=hOPtuGR1E5I&feature=BFa&list=ULOj-AO7B0jBk

Part 5: http://www.youtube.com/watch?v=Oj-AO7B0jBk&feature=BFa&list=ULhOPtuGR1E5I

Part 6: http://www.youtube.com/watch?v=a6ywpvS6Lsc&feature=BFa&list=ULOj-AO7B0jBk

Bill Nye: Greatest Discoveries : Evolution (Discovery Channel) - Extinction of

Dinosaurs, Origin of Life and Evolution

http://www.youtube.com/user/evolutiondocumentary?feature=results_main

Single Cell to Multicellular Organism

via extracellular matrix, such as collagen