In 2008, a re-analysis of Miller's archived solutions from the original experiments showed that 22 rather than 5 were actually created in one of the apparatus used.
At the end of one week of continuous operation, Miller and Urey observed that as much as 10–15% of the within the system was now in the form of organic compounds. Two percent of the carbon had formed that are used to make in living cells, with as the most abundant. Sugars, lipids, and some of the building blocks for nucleic acids were also formed.
NEIL DEGRASSETYSON: One of the most significantevents in our distant past is still perhaps the greatest mystery: the originsof life itself. How did it all get started?
Artificial selection shows the power of an outside selective force acting on a species, but that's not the only evidence for evolution. Other factors point to common origin for life forms. Bats, dolphins and people are all mammals, but bats fly, dolphins swim, and humans type, dine and doodle. If each species were carefully designed from scratch, there wouldn't be much need for overlap in skeletal structure. Yet all three types of animals share the same general limb design. Humans, dolphins and bats all have upper arm bones, lower arm bones, wrists, hand bones, and fingers. In dolphins, these bones are shortened to make a stiff flipper. Bats, meanwhile, spread their wings out over their finger bones.
DNA studies help humans find our own spot in the tree of life. Comparing the genetic material of humans and other great apes shows that our DNA differs within our own species by about 0.1 percent, with that of the chimpanzees by about 1.2 percent, and with that of the gorillas by about 1.6 percent. Yet humans and African apes (including gorillas) all share more similar DNA than the African apes share with orangutans, which dwell in Asia. Darwin predicted that humans branched off from other apes in Africa and modern studies back up his hypothesis.
As evolutionary biologists have pointed out, any of the experiments designed to test Darwin and Wallace's theory of natural selection since it was first proposed could have proven the hypothesis wrong. None of those tests did. So evolution is "just a theory" the same way that the theory of plate tectonics and the germ theory of disease are just theories. And gravity.
An assortment of tiny islands in the Bahamas recently gave researchers the chance to compare the roles of predation and competition in natural selection. The scientists stocked each island with lizards that they planned to observe, careful to ensure no reptilian island-hopping. Even before that, they measured and marked each lizard, and put each (un)willing experiment participant through a fitness test on a treadmill. Some islands were sparsely populated, meaning the lizards' biggest challenge was predation. Other islands were crowded, so the biggest challenge in those places was beating the other lizards to the most calories. At the end of breeding season, the researchers sifted through their results and discovered that competition for resources was a bigger driver of natural selection than predation. Local predators turned out to be unfussy eaters. The lizards that won the chow contest on crowded islands, however, were bigger and more athletic than the survivors on un-crowded islands.
And then there are genes that manage the big picture in a variety of organisms. First found in fruit flies, Hox genes regulate overall body plans for everything from bugs to birds. Although the genes differ between vertebrates and arthropods, they show remarkable similarities. They often occur together in a comprehensible order, in contrast with most other genes, and their order matters. Arguably grisly experiments with these genes show that moving them around creates fairly disgusting mutants, like flies with legs sprouting from their heads. Likewise, grafting mouse mouth tissue into a developing chick embryo demonstrates how Hox genes work across different animals; the resulting chicks hatch with teeth, though the teeth look dinosaurian.
In 2008, a group of scientists examined 11 vials left over from Miller's experiments of the early 1950s. In addition to the classic experiment, reminiscent of 's envisioned "warm little pond", Miller had also performed more experiments, including one with conditions similar to those of eruptions. This experiment had a nozzle spraying a jet of steam at the spark discharge. By using and , the group found more organic molecules than Miller had. Interestingly, they found that the volcano-like experiment had produced the most organic molecules, 22 amino acids, 5 and many molecules, which could have been formed by produced by the electrified steam. The group suggested that volcanic island systems became rich in organic molecules in this way, and that the presence of there could have helped these molecules form .
CHAD COHEN: ...they've filled in a piece of that mysteriousunderside to the tree of life, because, as we trace our origins by lookingdown, chemists like Sutherland are seeing things in a different way.
In recent years, studies have been made of the composition of the products of "old" areas in "old" genes, defined as those that are found to be common to organisms from several widely separated , assumed to share only the (LUA) of all extant species. These studies found that the products of these areas are enriched in those amino acids that are also most readily produced in the Miller–Urey experiment. This suggests that the original genetic code was based on a smaller number of amino acids – only those available in prebiotic nature – than the current one.
Conditions similar to those of the Miller–Urey experiments are present in other regions of the , often substituting light for lightning as the energy source for chemical reactions. The that fell near , Australia in 1969 was found to contain over 90 different amino acids, nineteen of which are found in Earth life. and other are thought to contain large amounts of complex carbon compounds (such as ) formed by these processes, darkening surfaces of these bodies. The early Earth was bombarded heavily by comets, possibly providing a large supply of complex organic molecules along with the water and other volatiles they contributed. This has been used to infer an origin of life outside of Earth: the hypothesis.