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BBC – Future – Will people reuse if we are still rethinking?

What happens if the hands of time return to an unreasonable point in our evolutionary history and start the clock again? American American paleontologist Stephen Jay Gould propose a well-known experimental thought in the late 1980s – and still covers the imagination of today's evolutionary biologists.

Gould noted that if the time is rewound, then evolution will strengthen life in a completely different path and people will never change. In fact, he felt that the evolution of humanity is so rare that we can replay the tape of life a million times and we can not see anything like Homo sapiens re-emerging.

is a major role in evolution. These include massive mass extinction events ̵

1; such as the effects of cataclysmic asteroids and volcanic eruptions. But chances of chance also operate at the molecular level.

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In other words, evolution is the product of random mutation. A rare few mutations can improve an organism's chance of survival in their surroundings with others. The split from one species to two starts from such rare mutations to be common over time. But additional random processes can still interfere, potentially leading to a loss of beneficial mutations and increasing harmful mutations over time. This inbuilt randomness should suggest that you get different life forms if you replay the tape of life.

Of course, in fact, it's impossible to restore the clock in this way. We will not know exactly how likely it is to be at this moment as we are. Fortunately, however, experimental evolutionary biologists have a way to test some of Gould's theories on a microscale with bacteria.

Microorganisms are divided and change very fast. We can freeze billions of identical cells in time and store them indefinitely. This allows us to get a subset of these cells, challenge them to grow in new environments and keep track of their adaptive changes in real time. We can go from "present" to "the future" and come back many times as long as we do not – it's important to replay the live tape in a test tube.

Many studies of bacterial evolution have been found, perhaps surprisingly, following the very predictable path in the short term, with both characteristics and genetic solutions often cropping up. For example, consider a long-term experiment, where 12 independent populations of Escherichia coli established by a single clone, have been continuously evolving since 1988. That's over 65,000 generations – there are only 7,500-10,000 generations since modern Homo sapiens appeared. All emerging populations in this experiment show higher fitness, faster growth and larger cells than their ancestors. It indicates that organisms have some barriers to how they will change.

Natural selection is the "guiding hand" of evolution, which reigns over the turbulence of random mutations and abetting useful mutations

There are evolutionary forces that maintain the developing organisms in the straight and narrow . The natural selection is the "guiding hand" of evolution, which prevents the excitement of random mutations and abetting beneficial mutations. This means that many genetic changes will disappear from existence over time, which is only the best of patience. It can also lead to both survival solutions realized in completely unrelated species.

We find evidence for this in the history of evolution where species are not closely related, but share similar environments, develop a similar character. For example, dead pterosaurs and birds are both developing wings as well as a unique beak, but not from a recent common ancestor. So important wings and beakers grew twice, in parallel, due to evolutionary pressures.

But the geneticist is also important. Not all genes are created equally: some have a very important job compared to others. Genes are usually arranged in networks, comparable to circuits, complete with redundant switches and master switches. The "master switch" mutations naturally result in much larger changes, due to the knock-on effect felt by all genes under its control. This means that some locations in the genome contribute more to evolution, or have a greater impact, than others – the aberration of the results of evolution.

But what about the underlying laws of physics – do they appreciate predictable evolution? In very large levels, it appears. We know many laws governing our universe that are certain. Gravity, for example – where we owe our oceans, thick environments and nuclear fusion to the sun giving us energy – is a predictable force. The theory of Isaac Newton, based on large-scale deterministic forces, can also be used to describe many systems in large scales. They represent the universe as perfectly predictable.

If Newton's perspective remains true, the evolution of humans is unavoidable. However, this entertaining predictability is dissolved by the discovery of a contradictory but incredible world of quantum mechanics in the 20th Century. At the smallest levels of atoms and particles, the real difference is in play – meaning our world can not be predicted at the very basic level.

This means that the broad "policy" for evolution will remain the same no matter how many times we replay the glue. It will always be an evolutionary advantage for organisms that reap solar power. There is always a chance for users of abundant gas in the environment. And from these adaptations, we can predict the emergence of familiar ecosystems. But ultimately, the randomness, which has been developed in many evolutionary processes, will remove our ability to "see in the future" with absolute certainty.

A problem with astronomy plays an appropriate role. In the 1700s, a mathematical institute offers a prize for solving a "three-body problem", involving precisely describing gravitational relationships and the resulting orbits of the sun, Earth and moon.

We may not be quite sure where we want to end if we rewind time, but the paths that are used to developing organisms are far from infinite

The winner is important to prove that the problem can not be resolved exactly. Like the disadvantages introduced by random mutations, a small startup error can not grow, meaning you can not easily determine which three bodies will end in the future. But as a dominant partner, the sun dictates the orbit of all three to a certain extent – allowing us to narrow the possible positions of the bodies within a range.

It is like the guiding hand of evolution, which corresponds to organisms in familiar routes. We may not be completely sure where we will end if we rework time, but the paths that are used to emerging organisms are far from infinite. And so maybe people will never appear again, but it's likely that any alien world is replaced by ours, it's a familiar place.

This article originally appeared at The Conversation, and was republished under a Creative Commons license.

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