Life Before Earth
Alexei A. Sharov, Ph.D., Richard Gordon, Ph.D.

Abstract
An extrapolation of the genetic complexity of organisms to earlier times suggests that life began
before the Earth was formed. Life may have started from systems with single heritable elements
that are functionally equivalent to a nucleotide. The genetic complexity, roughly measured by the
number of non-redundant functional nucleotides, is expected to have grown exponentially due to
several positive feedback factors: (1) gene cooperation, (2) duplication of genes with their
subsequent specialization (e.g., via expanding differentiation trees in multicellular organisms),
and (3) emergence of novel functional niches associated with existing genes. Linear regression of
genetic complexity (on a log scale) extrapolated back to just one base pair suggests the time of
the origin of life = 9.7 ± 2.5 billion years ago. Adjustments for potential hyperexponential effects
would push the projected origin of life even further back in time, close to the origin of our galaxy
and the universe itself, 13.75 billion years ago. This cosmic time scale for the evolution of life
has important consequences: (1) life took a long time (ca. 5 billion years) to reach the complexity
of bacteria; (2) the environments in which life originated and evolved to the prokaryote stage
may have been quite different from those envisaged on Earth; (3) there was no intelligent life in
our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with
life by intelligent aliens; (4) Earth was seeded by panspermia; (5) experimental replication of the
origin of life from scratch may have to emulate many cumulative rare events; and (6) the Drake
equation for guesstimating the number of civilizations in the universe is likely wrong, as
intelligent life has just begun appearing in our universe. Evolution of advanced organisms has
accelerated via development of additional information-processing systems: epigenetic memory,
primitive mind, multicellular brain, language, books, computers, and Internet. As a result the
doubling time of human functional complexity has reached ca. 20 years. Finally, we discuss the
issue of the predicted "technological singularity" and give a biosemiotics perspective on the
increase of life’s complexity.

(snip)

What is most interesting in this relationship is that it can be extrapolated back to the origin of life.
Genome complexity reaches zero, which corresponds to just one base pair, at time ca. 9.7 billion
years ago (Fig. 1). A sensitivity analysis gives a range for the extrapolation of ±2.5 billion years
(Sharov, 2006). Because the age of Earth is only 4.5 billion years, life could not have originated
on Earth even in the most favorable scenario (Fig. 2). Another complexity measure yielded an
estimate for the origin of life date about 5 to 6 billion years ago, which is similarly not
compatible with the origin of life on Earth (Jørgensen, 2007). Can we take these estimates as an
approximate age of life in the universe? Answering this question is not easy because several
other problems have to be addressed. First, why the increase of genome complexity follows an
exponential law instead of fluctuating erratically? Second, is it reasonable to expect that
biological evolution had started from something equivalent in complexity to one nucleotide? And
third, if life is older than the Earth and the Solar System, then how can organisms survive
interstellar or even intergalactic transfer?