Life began on Earth about 3.8 billion years ago, a mere 700 million or so years after the Earth was formed. However, these simple life forms remained mostly microscopic until about 570 million years ago. More » History Prehistory

While there are many theories as to how life began on Earth, no theory has been accepted as truth, according to NBC News. Biologist Diana Northup from the University of New Mexico says this is because it's hard to prove ... More »

Plant life first appeared on land during the Ordovician period, between 495 and 443 million years BCE. One 2001 study from Penn State University claims that plants and fungi first appeared on land 700 million years BCE, ... More »

The earliest fossil evidence found suggests that life has existed on Earth for 3.5 to 3.9 billion years. The surface of the planet was hypothesized to be inhospitable to all life until after the Late Heavy Bombardment, w... More »

Human beings are on Earth, as opposed to any of the other planets in the solar system, because it is uniquely able to support the development of life. Some scientists speculate that Earth hosts the only intelligent life ... More »

Life began on Earth 3.8 billion years ago, as BBC Nature explains. At that time Earth became home to single-celled prokaryotes. 2.1 billion years ago multicellular life began, and the first arthropods appeared 570 millio... More »

As of 2015, scientists believe the first animal on Earth was the comb jelly of the phylum Ctenophora. It is an ocean-dwelling, gelatinous organism whose length varies from less than half an inch to 16 inches. Until 2008,... More »