पृथ्वी पर जीवन के अस्तित्व का इतिहास

thumb|पृथ्वी पर जीवन के इतिहास का एक स्पाइरल के रूप में दृष्यात्मक निरूपण

## मूलभूत समयरेखा
पृथ्वी के 

4.6 बिलियन वर्ष इतिहास में जीवन का इतिहास इस प्रकार है-

* पिछले 3.6 बिलियन वर्षों तक, सरल कोशिकाएँ (prokaryotes);
* पिछले 3.4 बिलियन वर्षों तक, स्यानोबैकेटीरिया (cyanobacteria) प्रकाश संश्लेषण करता रहा;
* पिछले 2 बिलियन वर्षों तक, जटिल कोशिकाएँ (eukaryotes);
* for the last 1 billion years, multicellular life;
* पिछले 600 मिलियन वर्षों तक, सरल जन्तु;
* for the last 550 million years, bilaterians, water life forms with a front and a back;
* for the last 500 million years, fish and proto-amphibians;
* for the last 475 million years, land plants;
* for the last 400 million years, insects and seeds;
* for the last 360 million years, amphibians;
* for the last 300 million years, reptiles;
* for the last 200 million years, mammals;
* for the last 150 million years, birds;
* for the last 130 million years, flowers;
* for the last 60 million years, the primates, 
* for the last 20 million years, the family *[[Hominidae]]* (great apes);
* for the last 2.5 million years, the genus *[[Homo (genus)|Homo]]* (human predecessors);
* for the last 200,000 years, anatomically modern humans.

Periodic extinctions have temporarily reduced diversity, eliminating:
* 2.4 billion years ago, many obligate anaerobes, in the oxygen catastrophe;
* 252 million years ago, the trilobites, in the Permian&ndash;Triassic extinction event;
* 66 million years ago, the pterosaurs and nonavian dinosaurs, in the Cretaceous&ndash;Paleogene extinction event.
Dates are approximate.

## विस्तृत समयरेखा
In this timeline, **[[Year#SI_prefix_multipliers|Ma]]** (for *megaannum*) means "million years ago", **ka** (for *kiloannum*) means "thousand years ago", and **ya** means "years ago".

### Hadean Eon

4000 Ma and earlier.

### Archean Eon

4000 Ma &ndash; 2500 Ma

### Proterozoic Eon

2500 Ma &ndash; 542 Ma

### Phanerozoic Eon

542 Ma &ndash; present

The Phanerozoic Eon, literally the "period of well-displayed life", marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.

#### पुराजीवी महाकल्प

542 Ma &ndash; 251.0 Ma

#### मध्यजीवी महाकल्प

#### नूतनजीवी महाकल्प

66 Ma &ndash; present

##### ऐतिहासिक विलोपन (Historical extinctions)

## इन्हें भी देखें
* भूवैज्ञानिक समय-मान
* पृथ्वी का इतिहास
* कार्बन-१४ द्वारा कालनिर्धारण
* प्राकृतिक इतिहास

## पठनीय
* *The Ancestor's Tale* by Richard Dawkins, for a list of ancestors common to humans and other living species

## सन्दर्भ

## बाहरी कड़ियाँ
* Berkeley Evolution
* Evolution Timeline
* Tree of Life Web Project - explore complete phylogenetic tree interactively
* A more compact timeline at the TalkOrigins Archive
* Palaeos - The Trace of Life on Earth
* John Kyrk's Timeline from Big Bang to present
* University of Waikato - Sequence of Plant Evolution
* University of Waikato - Sequence of Animal Evolution
* Graphical Timeline of evolution 
* History of Life on Earth
* Exploring Time from Planck Time to the lifespan of the universe
* Interactive Plant Evolution Timeline - from the University of Cambridge Ensemble Project

श्रेणी:जीवन की उत्पत्ति