Re: WHY EVOLUTION IS NOT A DOWNWARD PROCESS?

Hi Souvik,
A complex animal like a bird with many adaptations for flight which you 
might consider to be "highly evolved" can lose those adaptations in 
habitats where they are no longer advantageous - e.g. ostriches.  Just 
because they have lost some adaptations for flight doesn't mean that 
evolution has "gone backwards", many, many gene mutations are necessary 
for something like flight to have evolved and it would be an incredibly 
complicated pathway to retrace in reverse, especially as every step along 
the pathway must have been advantageous at a particular time in the past.  
You are unlikely to get exactly the same environment and selective 
pressures acting in reverse, so the mutations that occurred to enable 
flight to evolve are unlikely to evolve in reverse.  Entirely different 
mutations may have occurred to make the ostrich flightless, it is not 
evolution going in reverse, just evolution going in a different direction.

Lots of plants and animals, some more complex than others all live 
together on our planet right now.  These animals and plants interact with 
each other and change each other's environments, humans are extremely good 
at changing our own environment to make it more suitable for humans (in 
the short term!) and often less suitable for other species - for example 
apes like chimpanzees and gorillas are becoming more and more endangered 
as humans destroy their habitats. 

Chimpanzees and gorillas are highly adapted for the habitats that they 
live in at the moment, they are not the same species that humans evolved 
from, the species that humans evolved from have gone extinct, perhaps 
because they were out-competed by modern humans or some other aspect of 
their environment changed and drove them to extinction.  We are just one 
twig on the tree of evolution, gorillas and chimpanzees are other, close-
by twigs, evolved from the same ancestor as modern humans but no closer to 
that ancestor than we are.  So even if evolution went in reverse we 
wouldn't become chimpanzees.

I can hardly imagine how incredibly complex the pathway all the way back 
to amoeba would be - and along that pathway are millions of other species 
all highly adapted to their environments and exploiting it far better than 
a "backwards evolved" human would.  Even the most lowly amoeba is doing a 
better job in the world at the moment than the common ancestor of humans 
and the modern amoeba, a "backwards evolved human amoeba" would be out-
competed very rapidly by the modern amoeba around at the moment.

I hope this answers your question - evolution is a fascinating and mind-
blowing topic!
Yvonne