Evolution insights presents evidence of new views of evolution as well as discussion of old and sometimes erroneous views. Other topics of interest to me, and I hope others, are interspersed; primarily views of God, creativity, and science. Current events, major and minor, are also distractions presented.
Evolution and Asteroid Strikes ASTEROID STRIKES HELPED SHAPE OUR EVOLUTION Where would we be without asteroid strikes?
We might still be here, but we would look entirely
different. Bombardment with asteroids
and other space debris was much more common a billion years ago. At that time life in our ancestral line had
reached a worm-like stage that also gave rise to some other forms less like our
egocentric selves. The bombardment had
an enormous impact on the course of evolution.
When God created the universe it began as a speck
over twelve billion years ago as we measure time. That speck was endowed with the properties
that would spawn several generations of stars and the galaxies we see
today. It had all the potential for the
formation of elements and star systems with associated planets as well as the
evolution of life as we know it. Darwin
realized this as the work of the Creator before events sped his drift into
I know, from the things science has discovered, some
major things that answer a few major evolutionary questions. It is not because of personal brilliance or
planning that I know them. It is not
because of some revelation that I know them.
It is the result of an unusual set of circumstances which I, have
blundered into and, now view as God’s direction of the chance events that made
it possible for me to put the bits of the puzzle together.
In 1987 two paleontologists (Raup and Sepkoski)
published a study of extinction rates that showed high peaks associated with
major asteroid impacts. A regression
line, which I calculated from their data, projected back over half a billion
years to the beginning of the Cambrian where it reached a 100% extinction
rate. That obviously did not occur
because there are Pre-Cambrian fossils, some of which had remains looking much
like tubes of pogonophorans, which still live in the abyssal regions of the
Pogonophorans were able to survive the Precambrian
bombardment because they had evolved by natural selection to survive by
absorbing nutrients from sediment and lost many of the typical annelid worm
features of their ancestors. They even
lost the mouth and rigid early embryological features of their ancestral annelids. Some changes now evident in their descendants led to, among other things- our systems being upside down as compared to most
worms, our fertilized egg’s ability to have each of the early cells survive as
twins or multiple births instead of dying when separated, and our pituitary to
have its peculiar blend of hormones (the endodermal and ectodermal tissues that
form the pituitary couldn't have joined if the pogonophoran pharyngeal region
had not been suppressed during the period the former circumesophageal nerves
Biologists think ancestral forms are replaced by new
forms and cannot be found unchanged today.
But pogonophorans, because of the peculiar features of the deep sea have
extremely long lives as individuals and thus those that stayed there evolved
Many astronomers have come to believe the moon (Wikipedia, moon formation) started as a result of a collision of the earth with another heavenly
body. They believe the probability is
very minuscule, but why bother when it is obvious that the following is much
more likely. The asteroid belt consists
of orbiting fragments from a collision of two or more planets, or a planet and
another major object, in that region between the orbits of Mars and
Jupiter. The scars on the moon, other
planets, and large asteroids show the evidence of past impacts. This immense accumulation of space debris was
sufficient to slow the moon’s rotation so gravity’s effect could bring it to
zero rotation with respect to the earth.
The earth’s greater mass was sufficient to keep it rotating even though
we probably received more mass from space than did the moon, slowing us from
400 plus rotations per year to 365.
Tidal friction is used to explain the slowing of rotation for both the
moon and the earth; but, shouldn't it have been more dramatically slowed for
the earth with its oceans if that were true?
So we have cleaned out most of the fragments in
earth’s orbital path and have a much reduced probability of an earth shattering
strike from outer space than in prehistoric times. The relative peace with the reduction or cessation
of celestial bombardment, the last really major event being the strike that helped end the dinosaurs at the end of the Mesozoic about sixty-five million years
ago, left a partial void that was repopulated in part by survivors from the
deep sea. The process of re-population from the deep-sea was much more important as the Cambrian began.
Incidentally, the idea of annelid worms being in our
ancestral line was much more popular a hundred years ago. Our annelid ancestry was rejected because of
the great differences in embryology of annelids as compared to the vertebrates
and invertebrates sharing our ancestral line starting with the
pogonophorans. When genetic information
helped us see that the embryological differences were not the complete answer,
the old annelid origin theory was not restored.
DNA/RNA studies are excellent for determining the relationships of
closely related organisms. Nucleic acid
studies, as currently performed, have not yet been refined enough to project distant
relationships. We know more about distant relationships from other data for
widely different groups.
Almost anybody can write a book. I've written a manuscript for one explaining some of the
above. But it runs counter to popular
opinion of most students of evolution.
Why? Probably because few
biologists today have time for the range of course work common in my
generation. I had to dig into the
literature on pogonophorans to revise an invertebrate zoology text for a second
edition that was published in 1968. I
found that they must live for several thousand or more years, thanks, in part, to my knowledge of marine biology. I might not have realized that if I hadn't developed an interest in causes of longevity during my doctoral studies (at
MSU) comparing Michigan and Tasmanian isopod crustaceans (thanks to a 1956 Fulbright
Grant for study at the University of Tasmania).
So the obscure pogonophorans that weren't even known
about a hundred years ago provide important clues. They show up in odd places in molecular
studies of evolution because they have changed only slightly genetically while
more recent groups have changed greatly.
Thus the great differences between the extremes of more recent groups are
greater than the difference between either of the extremes and the
pogonophorans. I know it is due to the
ancestral position of the pogonophorans and their extreme length of life. My evolutionary colleagues think it can be
explained away as an anomaly called “long-branch attraction”.
If my argument that major asteroid strikes are
remarkably less likely in the future than in the past does not comfort you,
consider the following. If strikes are
random, the likelihood of a strike is directly proportional to the area considered. The mid-February one exploded above
Chelyabinsk, Russia. On average, for every 63 that hit Russia, the largest
country in the world, only 36 would hit the United States; about 100 would hit
Russia while 1 is hitting Michigan; Liechtenstein would get about one strike
for every 100,000 to hit Russia.
Kalamazoo is smaller than Liechtenstein, so sleep well tonight. If you are still worried, remember that the
one hitting Russia is only about the second big one to hit in the past one hundred
and five years, the other knocked down trees over a large area in Siberia.
Oh, by the way, the regression line that I
calculated hit 100% extinction rate at the beginning of the Cambrian, if I
remember correctly, projecting forward, it did not hit zero anytime soon. But with strikes in our area likely to be
about once every twenty million years there doesn't seem to be much to worry
about if the injuries are no worse than in Chelyabinsk.
Joseph G. Engemann, Kalamazoo,
Michigan, Emeritus Professor of Biological Science, Western Michigan University. This was written for, but not sent, to the Kalamazoo Gazette letters editor in late February. Edited 5/11/13.