The Human Edge: Finding Our Inner Fish One very important human ancestor was an ancient fish. Though it lived 375 million years ago, this fish called Tiktaalik had shoulders, elbows, legs, wrists, a neck and many other basic parts that eventually became part of us.

The discovery of well-preserved pelves and a partial pelvic fin from Tiktaalik roseae, a 375 million-year-old transitional species between fish and the first legged animals, reveals that the evolution of hind legs actually began as enhanced hind fins.

Tiktaalik provides clues about a key transition in the history of life. Now extinct, this organism was a close relative of one our own ancestors — the first vertebrate to evolve four limbs and crawl out onto dry land.

Tiktaalik lived in marshy river settings resembling today’s Amazon. Up to 9 feet (2.7 meters) long, the lobed fish hunted like a freshwater crocodile in rivers and inlets, and had a surprisingly agile neck and primitive lungs.

The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared.

Since the extinction event that wiped out the dinosaurs 66 million years ago, fish have evolved and diversified, leading to the wide variety of fish species we see today. According to a new study, many of today’s fish lineages emerged right around this time. …

400-Million Year-Old Fish Discovered Is Ancestor of Dinosaurs, Humans. Paleontologists have discovered fossilized remains of the world’s oldest bony fish, which swam the Devonian seas 400 million years ago. As the earliest known bony fish, “Ligulalepis” is closely related to our own ancestors.

Land plants evolved from ocean plants. That is, from algae. Plants are thought to have made the leap from the oceans onto dry land about 450 million years ago. A single plant can produce thousands or millions of spores at once.

Soil is our life support system. Soils provide anchorage for roots, hold water and nutrients. Soils are home to myriad micro-organisms that fix nitrogen and decompose organic matter, and armies of microscopic animals as well as earthworms and termites. Soil plays a vital role in the Earth’s ecosystem.

The early phase of soil formation starts by disintegrating the rock under the influence of climate. Rainwater will dissolve rock elements, temperature fluctuations will cause cracks and fissures in the rocks. Freezing and thawing of water captured in the rock will widen existing cracks and cavities.

The four major processes that change parent material into soil and develop soil horizons are additions, losses, translocations, and transformations.