|
Plantsman wrote:
>
>Take cattle for example, as they have been domesticated in massive
>amounts for millennia. They have changed physically in size, shape,
>color & etc., slightly due to selective breeding, but they are all
>still are cloven hoofed furry animals that moo. Their udders
>haven't begun to relocate nor have they begun development of canine
>teeth (or any meaningful upper front teeth for that matter).
>They've always been ruminants with multiple stomachs and it doesn't
>look like that will ever change. No changes that would distinguish
>them as another or new developing species have occurred.
>
Perhaps there is no need for domesticated cattle to evolve any further
from their current state. There is no need to adapt, because normally
the correct conditions are always provided for them. Any environmental
stressors that would otherwise cause non-domesticated animals to adapt
or die are eliminated to maximize productivity.
>This is
>the case for all animals that are known to exist currently.
>Elephants are very much the same as they were three thousand years
>ago. Even in the case of Metasequoia glyptostroides (Chinese
>Redwood), it remains unchanged from the fossil record. Also the
>Coelacanth fish and Alligator for that matter.
>
It is easy to say that something is a living fossil because it appears
unchanged over a very long period of time. However, when you analyze
things further, there are still minor to drastic changes over this time,
though the general body plan remains the same. Though elephants haven't
changed over three thousand years, neither have the majority of
organisms living today. Evolutionarily speaking, this is a very short
period of time. Starting with the earliest known relatives of today's
elephants around 50 million years ago, elephants have experimented with
a variety of extreme adaptations over time. Some around 10-20 million
years ago had huge lower jaws modified into a shovel-like form,
presumably a specialized feeding adaptation. Some had upper tusks and
lower tusks. Some varied by the difference in tooth shape, again, a
feeding adaptation. Though it is easy to say the Alligator is unchanged
over millions of years, we have to look at this one closer as well. The
genus Alligator is a fairly recent 20-30 million year old branch off the
crocodilian family. Yes, for millions and millions of years, the
standard living crocodilian body shape is relatively unchanged for the
most part. If we could go back to the time of the dinosaurs, well over
65 million years ago, one could easily identify crocodilians living
then. But, looking at the fossil record, and even living representatives
of crocodilians, this group, like elephants, experimented with various
adaptations over time. One good example living today would be the
gharial, a crocodilian that has a very long, very skinny snout lined
with thin, needle like teeth. (most other crocodile teeth are pretty
blunt). The gharial's adaptation suits it well for quick maneuvers in
water, and capturing swift moving slippery fish, on which it feeds
exclusively.
>Just to add fuel to the fire: I heard awhile back that some
>scientists hypothesize that basically all species alive today have
>always been around and other, less flexible cousins became extinct
>for various reasons over time. Perhaps most ancient plants and
>animals will always be unknown due to fossilization never occurring
>or never being found. We may have only discovered a tiny amount of
>species that have existed and just got lucky with what we have.
>Scientists can't even agree on the dating methods of fossils. In
>any event, I don't think we'll ever know for sure.
>
Very true!!!! We can only make "educated" guesses based on what little
evidence we have, and what seems remotely plausable, assuming the
evidence is being analyzed correctly. Our knowledge has changed so
dramatically over the past century with regard to our understanding of
fossil and living organisms. Views of prehistoric beasts in the late
1800s are so different, and often seemingly ridiculous compared to
modern interpretations. Perhaps in another hundred years, humans will be
looking at the theories of today and laughing at our misguided views of
the world around us. At the same time, not knowing an organisms origin
or how it works only adds to its mystique and uniqueness, and therefore
it gains greater appreciation to those who become aware of its presence.
NOW, THE AROID CONTENT:
One might consider the genus Anthurium to be a large scale evolutionary
experiment. There are so many species in this genus with a huge
diversity of leaf shapes and habits. Perhaps this group of plants is
trying to figure out what is sucessful and what isn't. In a discussion
on this list several months ago about Philodendron espiritus-sanctii, it
was mentioned that this beautiful plant with its overly exaggerated
leaves was known in habitat by only a handful of individuals. Though
most people instinctively blamed human greed and habitat destruction for
this, I think someone suggested it may have been rare in nature for
other reasons, and questioned putting this plant into tissue culture, if
it was something that was naturally fading away because it wasn't meant
to be. Perhaps this is an example of a plant that was attempting to
adapt to its conditions but was unsucessful.
Adam Black
|
IAS on Facebook
IAS on Instagram
