Emergence of Multi-Level Biological Systems
More than a dozen intermediate stages of emergence
in the universe of matter
were required to evolve
multicellular life, and they all still play a role in everyday living
The many successive levels of emergence that led to life on the planet
Earth today cannot be known precisely. The short story, as best my
understanding of science can say, begins at the
“big bang” with quarks and gluons and strings (Oh My!). A
brief sketch of the many levels of emergence thereafter are outlined
- A couple of seconds after
the big bang, the quarks, gluons, leptons, etc. condensed into a dense
sea of disassociated particles such as neutrons,
electrons, positrons, and neutrinos.
- As the universe expanded and cooled over a few hundred thousand
many of these particles joined into the stable sets of neutrons,
protons, and electrons that we call atoms
– mostly hydrogen atoms with some helium and a tiny admixture of the
next lightest nuclei: deuterium, lithium and beryllium. None
of the other atomic elements, many of which are vital to life, existed
- Perhaps 600 million years pass and the universe continues to
cool until gravity exaggerates slight differences in the density of
matter in vast subregions of the universe
to create the third level organization: the first galaxies and stars.
- Deep inside these first-generation stars, gravitational
pressure created the enormous temperatures that ignite fusion
reactions. The lightest
nuclei, hydrogen and a bit of deuterium, fuse together to create
nuclei. This process continues, creating the elements up
to iron, including the majority of elements vital to life as we know it
carbon, oxygen, nitrogen, sodium, potassium, calcium, etc.
- However, some of the heavier elements also vital to life, such
iodine, are not created in first-generation stars because normal fusion
processes cannot create elements nuclei heavier than iron,
The heavier elements are created by neutron capture processes such as
those that take place in the brief, violent death of stars in
supernovas. Supernovas not only create many of the remaining heavy
elements, but also their violent explosions spew
these newly created elements out into interstellar space where...
- Time passes, stellar dust from supernovas
eventually condenses again by gravitational attraction to form second
generation stars with
planetary systems that include the full complement of chemical elements
for rock, water, air and, ultimately, life.
- In our own little solar
system much more, time passes and the earth cools enough for liquid
water to condense: liquid water without which life as we know
it cannot exist. All sorts of catalytic chemical reactions in the
earth’s oceans and
atmosphere create the early carbon-based compounds that slowly combine
to create successively larger and more complex organic compounds.
- Eventually small
protocells are thought to have arisen: water and complex
sets of organic chemicals that are surrounded by fatty acid membranes
that separate their inside from the different composition of the
external world. These bilipid
reminiscent of simple cells, but aren’t alive, i.e., they cannot gather
energy from the outside world nor can
they replicate. [Note: the details of this step are still speculative.
alternative "first step toward life" posits agglomeration of
on tiny grains of clay rather than inside bilipid vesicles.]
- Perhaps 3.8 billion years ago, unexplained “magic”
creates mechanisms for replication that allow the emergence of simple
- For a couple of billion years thereafter,
single cell organisms evolve dizzying complexity in many steps:
mitochondria and chloroplasts that had been free-living simple cells,
creating the nucleus, and so forth.
- About 3.5 billion years ago, cyanobacteria
evolved physically co-located cooperative relationships held together
secretions from the cells (e.g., gel or slime). These
are possibly the first step
toward multicellular life. They are believed to be responsible for
conversion of Earth's early
carbon dioxide atmosphere into the oxygen-rich atmosphere of today.
- Between a billion and 600 million years ago
true multicellular (Metazoan)
organisms evolve that develop from a single fertilized
cell and share the same DNA. The prior cooperative
colonies of single cell organisms such as biofilms, consist of many
single cell species each with its own independent genome.
From the early multicellular organisms to mammals, then
to humans, is yet another series of emergent levels too complex and too
poorly understood to explore in this brief story. [That is not to imply
understand levels 8-12 all that much better.]
All of the levels described above are
evident in every living cell or organism today. The
biochemistry that emerged in the Earth’s oceans clearly operates in
every cell. Virtually all of the energy
used by every living cell comes from that produced by nuclear fusion in
the sun and captured via photosynthesis in plants. All the
hydrogen in cells was created in the big bang itself.
And many of the random events that generate
novel mutations that evolution can exploit are due to UV radiation from
cosmic rays from distant galaxies, and neutrinos, some of which are
from the big bang itself! So, every one of the
dozen or so layers of emergent behavior still participate in a great
cosmic dance, one small figure
of which is Earth’s biosphere containing all the various species of
Including copper, zinc, tin, iodine, silver, gold, lead, and uranium,
many of which are needed for life. Zinc, for
example, is crucial to many DNA binding proteins that control gene
expression. Molybdenum is crucial to bacterial and eucaryotic
oxotransferase enzymes. Cobalt is crucial to some
methyltransferases. Copper is crucial to the function of
cytochrome c oxidase, a central enzyme in the generation of ATP in
For example, carbonyl sulfide (COS), a simple volcanic gas, induces the
formation of polypeptides from individual amino acids in water
solution. Science, vol 306,
8 October, 2004, pp. 283-286. For a more extensive review of the
geophysical, geochemical, and biological processes involved in this
long process, see the Review paper: Mineral evolution, Robert M.
Hazen, et al, American Mineralogist, Vol. 93, pp.
1693–1720, 2008 A
can be found here.
We don’t know the steps that led to the evolution of the
fantastic mechanisms dependent upon RNA, DNA, and proteins that
replication, hence life. The term “magic” simply reflects
that ignorance. It is not intended to endorse any particular belief
system, either scientific or theological
This time estimate is very imprecise in part because the earliest
metazoans were probably
small, soft, creatures that did not leave fossils.
Contact: sburbeck at mindspring.com
Last revised 10/6/2012