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:7/23/2015)... (NASDAQ: AWRE ), a leading supplier of biometrics software ... ended June 30, 2015.  Revenue for the ... 33% compared to $6.8 million in the same quarter last ... $0.3 million, or $0.01 per diluted share, which compared to ... period a year ago.  Lower revenue and ...
(Date:7/20/2015)... 20, 2015  Acuity Market Intelligence,s latest research ... of Commerce and Privacy" forecasts that between 2014 ... will be downloaded to smart mobile devices by ... market is projected to generate more than $67.9 ... seven-year forecast period.    "Biometrics is ...
(Date:7/9/2015)... Calif. , July 9, 2015  Unchained ... today announcing its acquisition of Avid Nano. Avid ... light scattering (DLS) systems.    Also ... smallest, fastest and easiest to use protein sizing ... that measures a protein,s hydrodynamic size, size distribution, ...
Breaking Biology News(10 mins):Aware, Inc. Reports Second Quarter 2015 Financial Results 2Aware, Inc. Reports Second Quarter 2015 Financial Results 3Aware, Inc. Reports Second Quarter 2015 Financial Results 4Aware, Inc. Reports Second Quarter 2015 Financial Results 5Aware, Inc. Reports Second Quarter 2015 Financial Results 6Biometrics on Smart Mobile Devices to Redefine Digital Identity with 12.9 Billion Biometric App Downloads between 2014 and 2020 2Unchained Labs just can't get enough, acquires Avid Nano, rocks out the new pUNk! 2
... for their first child go on to have fewer children ... is shown in a study from the Norwegian Institute of ... at the NIPHs Medical Birth Registry and the University of ... and subsequent births until 2003. This covers nearly 600 000 ...
... victims of climate change, rain forest peoples in Latin ... in international decision-making on climate issues. A major landmark ... UN Framework Convention on Climate Change will take place ... from 13 countries and experts will be participating in ...
... centuries: eyes really are windows of the soulor at least ... April 2008 print issue of The FASEB Journal ( ... probe eye drops thatfor the first timemake it possible to ... organisms using MRI. Current methods involve a risky, invasive, and ...
Cached Biology News:Fewer babies born after Caesarean delivery 2International workshop to address capacity building for rainforest leaders 2International workshop to address capacity building for rainforest leaders 3Harvard researchers publish MRI images of genes in action in the living brain 2
Other biology definitionOther Tags