As far as I can see , the "perfect" evolvement of an alien must observe the following criteria.
1.... The creature must breathe (preferably) air.
2.... T he being would be subject to the "square cube law". Accordingly the "visitor "would not be much larger than the largest human and may very
well be a little smaller.
Its a limiting factor you see ....if you double the height of a being and yet still maintain the same proportions then the weight will increas by a
factor of 800%.
If this sounds odd, imagine the average 150lbs man. For him to increase in height he must also increase in mass and weight.
The formula reads 150x2 squared,which in this case is 1200lbs.
This would make for a rather cumbersome weight to be carrying about and would create the obvious difficulties in the handling of small tools.
You cant repair a watch with a large wrench. Small parts require delicate handling for which the "mechanic needs reasonably small sensitive fingers
and use small , light tools.
3....The creature must also b a plant AND a meat eater.. The plant eater must spend ALL OF ITS TIME grazing on low protein foods. A meat eater is able
to spend time resting after it has dined. If a creature has adapted to a dual diet it is far superior to a meat eater or a grazer mainly because it
can survive famine.
It is the same creature that will eventually evolve to a stage where leisure time becomes available for the satisfaction of curiosity about its
enviroment. and purpose of life.
4.... The being must weigh at least 40 pounds according to the theoretical rules of biological construction. Its a scientific fact that the brain of
advanced and intelligent beings must have a high mental capacity and must weigh at least two pounds.. at least a 40 pound body would be necessary to
house the two pound brain.
5....Since the brain is the most important possession of intelligent beings, nature will have created a form of defence for it throughtout evolution
of the species, a type of armour to protect it from injury.. The most natural answer is a skull made of bone matter.
6...The basic rules of biological construction promote the use of two eyes and two ears. One eye would prevent the being from distance estimation
and would limit side vision... two eyes combine to form the proper three dimensional perception. Additional eyes would only confuse the messages
reaching the brain. A similar case is made out for two ears.
7... It would also be necessary for the eyes and the ears to be situated as near as possible to the brain (i.e. in the skull) in order that the
reception of danger signals and the appropriate muscular reaction may be shortened as much as possible.
8.... Our friend must have arms and legs ......... it must be able to move about or it could not gather materials to satisfy its needs. It will have
to have a pair of hands with bending fingers and thumbs to make for the most efficient use of tools.
In early evolution, the creature may have had four legs but it will soon learn to stand erect and the two unused limbs will evolve into hands if it
is to acquire the ability to construct things.
Only hands will suffice for construction........... a claw or beak or talon will not be able to do the tasks required niether will a tentacle.
9... The creature must be land orientated.l
There ya go .............Ive just described you and me
Reptiles ........naah, they just dont fit into the scenario do they. Well thats my opinion or is thre some other criteria I have missed which would
invalidate my presumptions ?