Re: Darwin and Punctuated Equilibrium
- From: John Harshman <jharshman.diespamdie@xxxxxxxxxxx>
- Date: Fri, 22 Jun 2007 22:50:44 GMT
Robert wrote:
On Jun 21, 6:53 am, Ron O <rokim...@xxxxxxx> wrote:
It is relative too. Darwin was confronted with the proposition that
the earth could be no more than 300 million years old. The estimate
came from physicists that didn't know about radioactive decay or
nuclear fusion. Geologists were claiming that the earth was probably
older, and Darwin was associated with them, but Darwin had to admit
that if 300 million years is all that he had, that is all that he
had. All evolution of life would be considered punctuated under this
limit. The punctuated evolutionary guys like Gould were claiming that
the rapid evolution that they were observing in the fossil record was
occurring within 10,000 and 100,000 years, and they were talking about
a few new bumps on a trilobite or some other noticable change in size
or shape of the type of specimens they were finding.
Here's interesting background on trilobites from www.TheDragonOption.com
The universe began approximately fifteen billions years ago
in the deafening lifeless silence of the big bang. Some ten billion
years later, the Earth made its debut. A billion years or so after
that, the first one celled organisms began our dance of life. That was
nearly four billion years ago.
As the Earth's crust cooled, it settled into continental
shapes somewhat similar to those we know today. Under the influence of
tectonic forces, these elevated fragments would periodically be forced
together to form supercontinents. These supercontinents would remain
intact for a few hundred millions years and then break apart into
their constituent continental fragments. Over time, this process of
congregating and dissociating would repeat itself over and over again.
Though its existence is debatable, a proto-supercontinent, Yilgarn,
may have formed as early as four and a half billion years ago, shortly
after Earth's formation. However, the first recognized supercontinent
was Vaalbara which coalesced around three billion years ago while
single celled organisms still ruled the planet. After its breakup, the
second supercontinent, Kenorland, was in formation some two and a half
billion years ago when multicellular organisms first appeared.
Kenorland, in turn, broke apart and was succeeded by the third
supercontinent, Nuna (also called Columbia), around one and a half
billion years ago. It then separated and reformed about one billion
years ago as the fourth supercontinent Rodinia which, in turn, lasted
for some two hundred and fifty million years before its dissolution.
Pannotia, also known as the Vendian supercontinent, may have briefly
appeared around six hundred million years ago, but its existence, like
Yilgarn's, is also disputed. Either way, from Yilgarn to Kenorland,
life was strictly unicellular, while from Kenorland through Pannotia
it remained close to the rudimentary multicellular stage.
All this, including Rodinia, is highly speculative. The farther back you
go, the less record we retain of continental arrangements.
It was not until Pangea, the fifth and final official
supercontinent which started to form around five hundred million years
ago that organisms began to evolve rapidly.
This is true for only for very odd senses of "started to form" and
"began to evolve rapidly". It does appear that the assembly of Gondwana
can be dated to around this time, but Gondwana is quite a different
thing from Pangaea.
Trilobites, arthropods
with large exoskeletons that bear a striking resemblance to today's
horseshoe crabs dominated the land. While early versions of these
extinct creatures were less than a millimeter long, later varieties
grew up to twenty-eight inches in length.
I don't know what this refers to either. What tiny trilobites does it
mean? The earliest trilobites are olenellids, which are generally of
moderate to large size. It was no trouble for me to find a 15mm specimen
of Fallotaspis, perhaps the oldest known genus.
Of note, some trilobites had
eyes with upwards of fifteen thousand microscopic lenses in each one.
They disappeared around the time that Pangea broke up into the sub-
supercontinents of Laurasia and Gondwana, around two hundred and fifty
million years ago.
This is not any event I reconize. The first bit of the breakup of
Pangaea would seem to be the separation of North America and the opening
of the North Atlantic. The second is the separation of Africa from the
rest of Gondwana and the opening of the South Atlantic and parts of the
Indian Ocean.
By then, evolution had unveiled fish, small
reptiles, and a wide spectrum of plant life which covered both land
masses. Amongst these reptiles were the theriodontias, our pre-
mammalian ancestors.
As Laurasia and Gondwana moved apart, the former heading
north and the latter moving south, dinosaurs ruled the Earth until
their extinction some sixty-five million years ago. By that time,
Laurasia had divided into the major northern continents we know today:
North America, Mexico, Central America, Europe and Asia (minus India).
Mexico is a continent?
Gondwana, on the other hand, would take another sixty million years or
so to regress into the southern hemisphere's major land masses: South
America, Africa, Australia and Antarctica. About half way through the
dinosaurs' age of domination, India, originally part of Gondwana,
broke apart from Antarctica and headed toward the northern hemisphere.
Along the way, about ninety million years ago, it dropped off
Madagascar by the southeastern edge of Africa before slamming itself
into Asia. During its journey, the six mile wide Chicxulub Meteor
landed near the Yucatan Peninsula, bringing the dinosaurs' reign to
and end. Thus began the age of mammals.
Quoted from:
www.TheDragonOption.com
For more about trilobites, see topic:
www.TheDragonOption.com/chapter3.html#topic02
.
- References:
- Darwin and Punctuated Equilibrium
- From: Rolf
- Re: Darwin and Punctuated Equilibrium
- From: Ron O
- Re: Darwin and Punctuated Equilibrium
- From: Robert
- Darwin and Punctuated Equilibrium
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