Navigation Links
Common descent


A group of organisms is said to have common descent if they have a common ancestor. In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool.

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 or LUA), that is, the most recent common ancestor of all currently living organisms, is believed to have appeared about 3.5 billion years ago (see: origin of life).

History

The first suggestion that all organisms may have had a common ancestor and diverged through random variation and natural selection was made in 1745 by the French mathematician and scientist Pierre-Louis Moreau de Maupertuis (1698-1759) in his work Vnus physique. Specifically:

"Could one not say that, in the fortuitous combinations of the productions of nature, as there must be some characterized by a certain relation of fitness which are able to subsist, it is not to be wondered at that this fitness is present in all the species that are currently in existence? Chance, one would say, produced an innumerable multitude of individuals; a small number found themselves constructed in such a manner that the parts of the animal were able to satisfy its needs; in another infinitely greater number, there was neither fitness nor order: all of these latter have perished. Animals lacking a mouth could not live; others lacking reproductive organs could not perpetuate themselves... The species we see today are but the smallest part of what blind destiny has produced..."

In 1790, Immanuel Kant (Knigsberg (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 1795, Charles Darwin's grandfather, Erasmus Darwin, 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 Crick have postulated that the universal common ancestor could have come from space (panspermia). He was led to this conclusion by the universality of the genetic code (see below).

Evidence for common descent

Universality and similarity

The universality of the genetic code is generally regarded by biologists as definitive evidence in favor of the theory of universal common descent (UCD) for all bacteria, archaea, and eukaryotes (see Three domain system). Analysis of the small differences in the genetic code has also provided support for UCD.The Tree of Life Web Project


'"/>


(Date:11/15/2014)... YORK , Nov. 13, 2014  While we may ... technology Doctor McCoy used in "Star Trek" to gain instant ... tools designed to work with smartphones and tablets for monitoring ... of the healthcare world. This may seem a tad Orwellian ... ready to adopt some of these technological opportunities into their ...
(Date:11/10/2014)... detergent pods began appearing on U.S. store shelves in ... numbers ever since. The small packets can be tossed ... out a liquid or powder. The convenience, though, has ... study from researchers at Nationwide Children,s Hospital found that ... reports of 17,230 children younger than 6 years of ...
(Date:11/7/2014)... -- Leading Biometric companies aim to provide consumers ... transactions.  Companies in focus today are: NXT-ID, Inc. (NASDAQ: ... ), Google Inc. (NASDAQ: GOOG ), Microsoft Corporation ... EBAY ) and MasterCard Inc. (NYSE: MA) NXT-ID, ... authentication company focused on the growing mobile commerce is pleased ...
Breaking Biology News(10 mins):Americans May Be Ready for a Brave New World of Healthcare 2Americans May Be Ready for a Brave New World of Healthcare 3Americans May Be Ready for a Brave New World of Healthcare 4Study finds laundry detergent pods, serious poisoning risk for children 2Universal Authentication Methods Provide More Secure Operations for Biometrics Devices - Company Joins FIDO Alliance for Consumer Protection 2Universal Authentication Methods Provide More Secure Operations for Biometrics Devices - Company Joins FIDO Alliance for Consumer Protection 3Universal Authentication Methods Provide More Secure Operations for Biometrics Devices - Company Joins FIDO Alliance for Consumer Protection 4Universal Authentication Methods Provide More Secure Operations for Biometrics Devices - Company Joins FIDO Alliance for Consumer Protection 5Universal Authentication Methods Provide More Secure Operations for Biometrics Devices - Company Joins FIDO Alliance for Consumer Protection 6
... 2011 (Rome, Italy) -- Researchers speaking in the second ... Pathogenesis, Treatment and Prevention (IAS 2011) have today provided ... and alerted delegates to the challenges that developing countries ... antiretroviral therapy (ART) coverage. The presentations reflect the ...
... Small-scale fisheries could pose a more serious threat to ... University of Exeter, published today (19 July) in the ... shows that tens of thousands of turtles from across ... small-scale fisheries. Focusing on fisheries in Peru, the ...
... use various appendages to move across surfaces prior to ... jerky form of movement known as "twitching" motility, which ... called type IV pili, or TFP. ... a professor of bioengineering and of chemistry and biochemistry ...
Cached Biology News:Plenary speakers address challenges in the delivery of sustained antiretroviral therapy in developing countries, call for social scientists to take their place at the HIV/AIDS policy-making table, and stress the need for a long-term response to AIDS 2Plenary speakers address challenges in the delivery of sustained antiretroviral therapy in developing countries, call for social scientists to take their place at the HIV/AIDS policy-making table, and stress the need for a long-term response to AIDS 3Study shows small-scale fisheries' impact on marine life 2UCLA study shows bacteria use Batman-like grappling hooks to 'slingshot' on surfaces 2
Other biology definitionOther Tags