On Mon, 13 Oct 2003 23:16:46 +0000 (UTC), [email hidden]
Quoted message said:
Quoted message said:Quoted message said:Popular writers often use the word adapt to imply passing on something that was not inherited,
but I think this smacks of Lamark.
So in the context of evolution, what is adaptation?
Quoted message said:Adaptation is a very general term for a change in a cell, an organism, or a population (species)
over time to adjust or modify some aspect of its behavior or function to the environment.
There is sensory adaptation where a sensory neuron ceases to respond (or responds more weakly) to
a sustained stimulus. The time scale may be on the order of seconds. There is physiological
adaptation to environmental circumstances that occurs on the time scale of seconds or minutes to
days and months. There is evolutionary adaptation that occurs over generations and is expressed as
changes in the genetic information.
So when you say "popular writers often use the word..." are you meaning only the latter notion,
the evolutionary notion, or are you including all the myriad other uses of the notion of
adaptation? I have never heard of the usage referring to "passing on something", though. Could you
provide some examples (with citations of source)?
You do also realize, of course, that many "popular writers" are simply careless or even incorrect
in their use of scientific notions.
Here is a suitable example with citation:-
``adúapútaútion:
Biology. An alteration or adjustment in structure or habits, often hereditary, by which a species
or individual improves its condition in relationship to its environment.''
- dictionary.reference.comsearchOpen ↗
An alteration or adjustment in structure sounds like the giraffe's neck getting longer as it
reaches for the higher branches. I understand that Lamark suggested that this longer neck would be
passed on.
A change in habit suggests that the organism was always able to behave in the new way, but did not
previously have a reason to do so.
Taming of wild animals might be an example of adaptation, but the offspring of abandoned pets seem
not to inherit any attraction to humans, suggesting that learned behavior is not automatically
passed on.
The dictionary suggests that adaptations are hereditary (passed on), but where is there
evidence of this?
I feel comfortable explaining the concepts of mutation and natural selection, but adaptation?
Again, your discomfort comes from the many different ways the word is used. As Wirt Atmar has
already pointed out, there is a strong and growing tendency to use the word purely in the
evolutionary sense. All the other physiological uses are supposed to be deprecated (although sensory
adaptation is likely to remain for a substantial period of time).
Looking into dictionaries isn't going to give you the real scientific usage and especially won't
give you the shift in usage towards the strictly evolutionary sense in the last few decades. I was
hoping for a citation from the scientific literature.
Since evolution is necessarily about heritable change, adaptations in that sense must be inherited.
The evidence is another story. There are two types of work required: showing that a trait is
inherited and showing that it has adaptive significance. Very often, something that "looks useful"
is simply assumed to be an inherited factor that, indeed, is useful. However, unless there is good
evidence, the notion is considered merely a "Just So" story.
It is not always easy to show that a particular character is, in fact inherited. It doesn't take
that much to demonstrate that the long neck of a giraffe is inherited but many things are less
certain. Humans today are significantly larger than our recent ancestors of even a few hundred years
ago. Look at the size of old suits of armor or of beds or the height of doorways That seems to be a
change in nutrition. Humans today have a longer life span than our ancestors. That seems to be a
change in public health measures and medicine. We run faster and jump farther and higher. That seems
to be due to training and the ability to pick the best athletic prowess from a much larger potential
pool of talent.
Showing that a feature is truly adaptive, that is, gives its owner some benefit -- increases its
fitness -- is usually even more difficult. For example, there is some evidence that the neck of a
giraffe is NOT primarily for feeding from high trees but is related to
indicates that giraffes do not, in fact, normally feed high up in trees. Instead the males use their
necks in combat, fighting for mates. But these are well known problems in physiological ecology or
animal behavior or evolutionary biology. A lot of people are very uncomfortable with the careless
use of the "just so" story and the casual assumption of the benefir and heritability of all sorts of
traits. Pinning down the details is enormously difficult and time-consuming work!
