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A theory of universal common descent based on evolutionary principles was proposed by Charles Darwin in his book The Origin of Species ( 1859), and later in The Descent of Man ( 1871). This theory is now generally accepted by biologists, and the last universal common ancestor (LUCA), that is, the most recent common ancestor of all organisms, is believed to have appeared about 3.5 billion years ago (see: origin of life).

1 History

The first suggestion that all organisms may have had a common ancestor seems to have been made in 1745 by the French mathematician and scientist

In 1790, Immanuel KantImmanuel Kant ( April 22, 1724 February 12, 1804) was a Prussian philosopher, generally regarded as the last major philosopher of the Enlightenment, having a major impact on the Romantic and Idealist philosophies of the 19th century, and as one of history (Königsberg (Kaliningrad) 1724 - 1804), in his Kritik der Urtheilskraft, states that the analogy of animal forms implies a common original type and thus a common parent.

In 1795Events January 16 French occupy Utrecht, Netherlands. January 20 French troops enter Amsterdam and later proclaim Batavian Republic. January 23 Dutch fleet freezes in Issel Meer. February 7 The 11th Amendment to the United States Constitution is passed., Charles Darwin's grandfather, Erasmus DarwinErasmus Darwin ( December 12, 1731 April 18, 1802) trained as a physician and wrote extensively on medicine and botany, as well as poetry. Living in Birmingham and Lichfield, England. He was one of the founder members of the Lunar Society. He was a member, hypothesized that all warm-blooded animals were descended from a single "living filament":

"...would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which THE GREAT FIRST CAUSE endued with animality...?" (Zoonomia, 1795, section 39, "Generation")

In 1859, Charles Darwin's The Origin of Species was published. The views about common descent expressed therein vary between suggesting that there was a single "first creature" to allowing that there may have been more than one. Here are the relevant quotations from the Conclusion:

"[P]robably all of the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed."

"The whole history of the world, as at present known,... will hereafter be recognised as a mere fragment of time, compared with the ages which have elapsed since the first creature, the progenitor of innumerable extinct and living descendants, was created."

"When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Silurian system was deposited, they seem to me to become ennobled."

The famous closing sentence describes the "grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one." The phrase "one form" here seems to hark back to the phrase "some few beings"; in any case, the choice of words is remarkable for its consistency with recent ideas about there having been a single ancestral "genetic pool".

More recently, scientists such as Francis CrickFrancis Harry Compton Crick OM ( June 8, 1916 July 28, 2004) was one of the discoverers of the structure of the DNA molecule. Born in Northampton, England, he studied physics at University College London, and became a B. During World War II, he worked on have postulated that the universal common ancestor could have come from space ( panspermiaPanspermia is a theory (more directly described as a hypothesis, as there is no compelling evidence yet available to support or contradict it) that suggests that the seeds of life are prevalent throughout the Universe and life on Earth began by such seeds). He was led to this conclusion by the universality of the genetic codeThe genetic code is a set of rules, which maps DNA sequences to proteins in the living cell through the mechanism of protein synthesis. Nearly all living things use the same genetic code, called the standard genetic code and all use small variations of it (see below).

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