What are oldest life forms on earth?

Answer 1

In its 4.6 billion yearscircling the sun, the Earth has harbored an increasing diversity of life forms:

• for the last 3.6 billion years, simple cells(prokaryotes);
• for the last 3.4 billion years, cyanobacteriaperformingphotosynthesis;
• for the last 2 billion years, complex cells(eukaryotes);
• for the last 1.2 billion years, eukaryotes which sexually reproduce
• for the last 1 billion years, multicellular life;
• for the last 600 million years, simple animals;
• 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 (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-Triassic extinction event;
• 66 million years ago, the pterosaurs and nonavian dinosaurs, in the Cretaceous-Paleogene extinction event.

all dates are approximate

Answer 2

Some of the oldest life forms on Earth are stromatolites, which are rock-like structures created by cyanobacteria. These organisms have been around for millions of years and are one of the earliest forms of life on our planet. Another ancient life form is the bacterium known as Thermotogales, which dates back to around 3.2 billion years ago.