As
I understand-
1.
Evolution is not a directed phenomenon. It is a very random process. Fitness is
determined not by the character in itself but by its usefulness in a given
environment. Thus a character which gives maximum benefit today may become
useless if there is change in environmental conditions. Changes in environment
are very random and sometimes very drastic. Such sudden changes may lead to
fixing of a given trait or removal of it from a population. Historically there
have been many such drastic changes in environmental conditions- ice age for
example. Earth's magnetic field direction also flips periodically. Creation of
new geographical topologies has occurred time and again. Such changes lead to
geographical isolation of populations which experience different micro and
macro climates leading to speciation.
2.
Humans are not descendants of modern day monkeys. It is a simplified way of
expressing a complex phenomenon. What it means is that modern day monkeys and
humans had a common ancestor just like modern day amphibians and pisces had
common ancestors. While drawing lineages in an evolutionary tree if the
common ancestor is unknown it is represented as the 'last unknown common
ancestor' and when known then they are called, Last Universal Common Ancestor
(LUCA).
If
you study all the fishes in the world today (and the found fossils) then you
will definitely see a gradation in use of gills, skin and lungs for breathing.
Therefore it is possible that fishes that use lung like structures and animals
that use lungs for breathing had a common ancestor. This ancestor population
underwent different degrees of isolation and exposure to environmental
conditions such that over a period of time its fragmented and segregated
population started looking like different species. The populations could no
longer interbreed even when put together. Some characters got fixed some
eliminated. Remember the word Fixed. Characters are not becoming better. Fixing
of characters may happen to different degrees. For instance, if the environmental
constraints are severe and selective for fast running then only the fastest
runners in a population will be able to survive. If the selective environmental
forces are not severe then sub populations with varying running speeds will
survive. If the selection pressure continues then the character gets
hyper-selected for.
[If
none of the sub populations have the running trait, then the species goes
extinct. It does not matter at that point of time if they were excellent
climbers. Thus it is the environment that selects!]
The
surviving population is then considered to have adapted. Not because it
suddenly started running fast, but because in its population there existed a
variant in character that enabled it to survive the change in external
conditions and therefore the continuation of the species. Therefore the
term survival cannot be applied to an individual animal. It is the species that
adapts and survives.
Lamarckism
is different in the sense that it tries to say that characters are acquired in
a lifetime. Experiments have failed in proving it to be the case.
3.
How the variants exist in a population can be explained to a certain extent
through breeding mechanisms employed (for instance sexual vs asexual) , genetic
mutations, gene swapping , allele cross-overs during meiosis (egg and sperm
formation) and so on.
4.
An example of evolution happening in real time is the development of
drug-resistance in microbes and pests such as mosquitoes.
5.
Some animals like cockroaches and horse shoe crabs are called living fossils.
They have been able to survive all the environmental changes for millions of
years without loss or fixing of any traits. Therefore not much change is
seen between fossils and present day living creatures.
6.
Evolution is often used as a positive word, as in to mean that traits become
better. But I feel Darwin would have objected. Because he took on a world which
believed in determinism- God created Man in his own image kind of thoughts. Or
in other words he faced a lot of opposition not for saying that man and monkeys
evolved. But because he questioned the very thought that Man was the best
creature. I feel it is ironical and sad that his theories are now twisted to
create a human-centric world view. He never said species evolve for the better.
He just said species bred, adapted, survived and evolved. Darwinism can also be
used to explain the existence of ethically accepted bad characters such as
bullying, cowardice, cheating etc.
