Whether or Not Last Universal Common Ancestor Is Even
Summary: Last Universal Common Ancestor has been held to be the common
ancestor of all the organisms that are known to exist on Earth. However, it is
not correct and therefore ruled out.
The idea of there being a Last Universal Common Ancestor (LUCA) also known
as Last Universal Ancestor (LUA) arose as a corollary to Charles Darwin’s theory
of evolution. It is also described as Most Recent Common Ancestor (MRCA) of
all current life on earth. Charles Darwin twice stated in his book ‘On the Origin
of Species’ about LUCA:
“Therefore I should infer from analogy that probably all the organic
beings which have ever lived on this earth have descended from some one
primordial form, into which life was first breathed”
“There is grandeur in this view of life, with its several forms, having been
originally breathed into a few forms or into one”
Scientific papers abound describing improbability of any other possibility as
well as features of LUCA. Wikipedia contains a list of 22 features of LUCA as
reported in various scientific papers. As recent as 2010, Hesman Saey, T. in
Discovery News has claimed a very high improbability of any other possibility
on mathematical-logical basis.
In 1998, Carl Woese proposed that no individual organism can be considered
as LUCA. He rather suggested community of organisms. In May 2010, Steel,
Mike and Theobald, Douglas L. based on “vast array of molecular sequences
now available from all domains of life” proposed a formal test of common
ancestry. However, the formal test did not require LUCA to be single organism,
but allowed it to be a population of organisms with different genotypes that
lived in different places and times. The formal test is also compatible with
multiple populations with independent origins (Ref. Wikipedia: Last Universal
Distribution of life: Life is widely distributed on the surface of Earth, above the
surface of Earth and below the surface of Earth. Life has been reported to exist
as much as 41 Km above the surface of Earth in atmosphere and 10 Km below
the surface of Earth in deep oceans. Barophillic Marine microbes have been
found at more than 10 Km depth in Marianas Trench. Culturable Thermophillic
microbes have been extracted from cores drilled more than 5 Km into Earth’s
crust in Sweden (Gold, 1992; and Szewzyk, 1994, both in PNAS). Life is known
to exist at temperatures as high as 122°C (Methanopyrus kandleri, Strain116).
Life is known to occur in vastly different habitats and so life forms range from
extremophiles - capable of living in extreme environments to parasites capable
of existence only in highly protected and specific environments provided by
The bottom line is that in order to keep existence, all life forms have to be
either well adapted or potentially adaptable to conditions of their existence.
No life form can ever exist for even brief periods under conditions to which it is
neither adapted nor adaptable.
Therefore existence of LUCA means existence of an organism that was able to
survive across the entire biosphere or exist in all habitats in which life is
presently known to occur.
So far none of the biologists have addressed themselves this question.
But on the basis of behavior of known life forms, it is hardly imaginable that
there could have ever been an organism capable of surviving in all habitats that
Alternatively, it may be said that Last Universal Common Ancestor, originated
at one or the other place and then gradually and over an immense period of
time dispersed to the entire biosphere. But such an eventuality in highly
improbable, keeping in view inability of organisms to survive in environments
to which they are neither adapted nor adaptable. Therefore it requires
hysterical dissociation of beliefs to believe that entire biosphere came to be
populated by the simple process of dispersal/migration of LUCA.
Moreover if Last Universal Common Ancestor was capable of surviving across
the entire biosphere, than what was the drive to further evolution in the light
of Darwin’s Theory of evolution? Since, according to currently popular theories
about evolution, improved adaptation leading to success in survival struggle
was the goal and objective of progressive evolution, with imperfect forms
trying to perfect themselves.
What is even more difficult to explain is migration of LUCA and its descendents
to a depth of 5 Km into Earth’s crust and vice-versa.
Therefore, the so called LUCA is nothing but scientific fiction created to fill gaps
in the theory, since rationally speaking, there can’t be a single organism that
could exist across the entire biosphere or its descendents would be able to
populate the entire biosphere as they evolve.
Hence LUCA is not even probable.
Therefore life must have originated in all habitats in which it could possibly
originate, satisfying all the conditions mandatory to origin of life. No doubt
that these mandatory conditions are presently unknown or have not been
Author: Dr Mahesh C. Jain is a practicing medical doctor and has written the
book “Encounter of Science with Philosophy – A synthetic view”. The book
begins with first chapter devoted to scientifically valid concept of God and
then explains cosmic phenomena right from origin of nature and universe up
to origin of life and evolution of man. The book includes several chapters
devoted to auxiliary concepts and social sciences as corollaries to the concept
of God. This is the only book which deals with origin of nature and universe
from null. Twenty-ninth chapter of the book deals with the subject matter of
‘Origin of Life’.