But where exactly might this have occurred—can we identify candidates for the role of Darwin’s ‘warm little pond’? Sleep et al.(Stanford) argue that a suitable environment might have been provided at submarine hydrothermal vents above serpentinite rocks, where chemical gradients of dissolved hydrogen gas and hydrogen ions could have provided a source of chemical free energy. Primitive life might have been established in pores contained within vent chimneys.
For decades the origin and evolution of life was restricted to the fossil record that recorded hard-shelled life. We now know, through determination of absolute ages by radioactive decay, that this record only record the last 500 m.y. or so of life. Prior to that, life existed as soft-bodied organisms, or even earlier, as single cell bacteria (prokaryotes) or single-celled organisms with nuclei (eukaryotes).
Behe suggests that the parts of irreducibly complex biological structures would be useless unless they appear all together, and evolution has no mechanism to build complex structures like this. Natural selection, after all, works just one step at a time...As Scott Gilbert shows in his textbook Developmental Biology, Eighth Edition, the evolution of the interconnecting bones of the middle ear illustrates how supposedly irreducibly complex structures can in fact be generated by the stepwise process of gradual change and natural selection.
More than 500 million years ago, single-celled organisms on Earth's surface began forming multi-cellular clusters that ultimately became plants and animals. Just how that happened is a question that has eluded evolutionary biologists.Now scientists have replicated that key step in the laboratory using common Brewer's yeast, a single-celled organism. The yeast "evolved" into multi-cellular clusters that work together cooperatively, reproduce and adapt to their environment--in essence, they became precursors to life on Earth as it is today.
Life! It's everywhere on Earth; you can find living organisms from the poles to the equator, from the bottom of the sea to several miles in the air, from freezing waters to dry valleys to undersea thermal vents to groundwater thousands of feet below the Earth's surface. Over the last 3.7 billion years or so, living organisms on the Earth have diversified and adapted to almost every environment imaginable.
Most people would consider such fundamental theories to be sufficiently tested by empirical evidence to conclude that they are indeed facts. As a result of the massive amount of evidence for biological evolution accumulated over the last two centuries, we can safely conclude that evolution has occurred and continues to occur. All life forms, including humans, evolved from earlier species, and all still living species of organisms continue to evolve today. They are not unchanging end-products.
Born 200 years ago, Darwin's revolutionary ideas were derived largely from his observations on life forms that evolved relatively recently, including various flowering plants, worms, birds and domesticated animals. Yet, life appeared on planet earth close to 4 billion years ago in the form of unicellular organisms collectively called bacteria...Today, microbes offer extraordinary testimony and powerful model systems of direct relevance to the essentials of Darwinian selection, such as understanding microbial host interactions, the evolution of pathogens and the emergence of drug- or vaccine-related resistance.
There are three features of the public goods hypothesis. Firstly, segments of DNA are seen as public goods, available for all organisms to integrate into their genomes. Secondly, we expect the evolution of mechanisms for DNA sharing and of defense mechanisms against DNA intrusion in genomes. Thirdly, we expect that we do not see a global tree-like pattern. Instead, we expect local tree-like patterns to emerge from the combination of a commonage of genes and vertical inheritance of genomes by cell division.
Despite thermodynamic, bioenergetic and phylogenetic failings, the 81-year-old concept of primordial soup remains central to mainstream thinking on the origin of life. But soup is homogeneous in pH and redox potential, and so has no capacity for energy coupling by chemiosmosis. Thermodynamic constraints make chemiosmosis strictly necessary for carbon and energy metabolism in all free-living chemotrophs, and presumably the first free-living cells too.
Abundant life appears to have colonized the Earth by approximately 3.8 Ga and to have evolved far beyond the ‘RNA world’ by this point in the Earth history. Evidence is provided only by the most durable bio-signatures that survive extensive metamorphism.
Asteroidal bombardment continued between 4.5x10^9 and 3.8x10^9 ybp while the Earth differentiated into core and mantle and degassed, forming the early atmosphere. It was during that turbulent period that life on Earth originated. It probably originated not just once, but many times, and in many different places, only to be stressed or even wiped out by the next asteroidal impact. About 3.8x10^9 y ago the asteroidal bombardment petered out, and life took firm hold on the surface of the young Earth.