How could it be that the Homo Erectus who had a brain size about half our size had their brain size doubled in us, with billions of extra neurons added?
Homo Erectus has lesser brain than Homo Sapiens this true, but Homo Erectus didn't evolve into anything, and it is another branch of the hominid family that just got extinct. (look the Wikipedia page for references)
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Could a single mutation of the DNA be enough for such a large change to occur?
most changes required to affect a permanent significant trait require a mixture of genes working together, however mutations of genes are cumulative and significant modifications of genes in a preserved gene pool are most likely to be reserved
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what about the new features added to an organism, like the ability of the human eye to see colors, the wings added to the birds, etc?
eyes and wings don't pop out to life because of a sudden gene or a group of genes changes.
if we are to give an explanation for the formation of the wing for example lets think like this:
squirrels don't have wings
most squirrels live high on trees
falling from trees or getting to trapped at some tree by a snake will most likely get the squirrels some trouble
squirrels are a member of the sciurids family (google it)
in deference to the rest of the sciurids family squirrels have wide tails because all others nearly are ground active and a great tail well cause them problems digging and running, while for squirrels a big tail mean better air resistance and less tendency to fail(think balancing beam)
http://graphics8.nytimes.com/images/2006/12/13/science/13mammal.l.jpgsome squirrels today, known as the flying squirrels have skin grown between their legs and hands and around the neck which gives them even greater air resistance, resulting in their ability to climb higher and jump between distanced trees
after several thousands generations every mutation in the flying squirrels members leading in a greater size of the skin parachute, or in softer hair, or in less bone weight will be amplified since those members will be capable to "fly' further and climb higher from all others
so in the next thousands generations you can find some descendants of this animal with more aerodynamic features that might be distant to create some sophisticated organic structure adding more to the flight capability
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eyes and in the same way could be formed as the following:
some cells developed sensitivity to light by means of a gene mutation(think a thermal neural cell for example)
organs having those kind of cells are most likely to overcome dangers and find food easier
more and more mutations and time might add to the size and sensitivity of the cells resulting in better capabilitis
p.s. such cell light sensitivity is found in nature in simple organisms even today
while cell receptions is good, but it is not that directional aware, but if a small curvature of such sells can happen by a gene mutation, this curvature will enable the organism to decide from what direction is the light coming from
same as wing formation with more curvature more survival odds are in for the animal and thus more gene prominence
while more curvature will help the animal, a cover is required for it not to get shut by other objects(transparent of course)
more curvature means information, more transfer nerves is a plus, and brain modification for analysis is also a plus
the cover of the curvature while maintaining transparency will need structural support, which will mean more thickness at least at the sides
cover need for blood will mean fluid being in the cover, ill fluid management will mean fluid is present in more quantities, and the cover being harder at the sides will make the fluids group in the middle
fluid in the middle of the cover will make a lense, resulting in better light reception
etc
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Where does the knowledge to create these new organs come from?
no where, the comparative advantage makes them to happen
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2) My understanding is that a random mutation causes a change in a species to occur, and then natural selection helps spreading this change out and eventually speciation occurs where the ancestor species and the new species can no longer reproduce.
this also include separation by geographical means for example
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How could random mutations have been so successful to consistently produce the various very complex traits found in the species? E.g wings, long neck of the giraffe, stripes of the zebra, claws and the strength of lions & tigers which make them more effective than smaller cats, etc?
stripes on the zebra are of no practical use as i know, but can be a by-product of some gene mutation that had another beneficiary effect.
however for the lions and all the great cats size i obviously a competitive advantage that can make the animal chances at survival better, thus if before several thousands of generations some group of cats developed a gene mutation that affected them to grow slightly larger, those animals are more likely to be successful and thus will get a better chance ti survival...and every time a gene mutation happened that correlated with a bigger size this mutation will be reserved, any other mutation that resulted in smaller size would had been got out of the way simply......and same goes with the nick length
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3) How did random mutations helped in the evolution from the earliest bi-polar apes (e.g Lucy) to homo erectus, to human beings, etc? Was it just random mutations that caused homo erectus to lose their body hair, or was there a controlled process behind it which knew that less hair would be more beneficial? Please clarify.
humans are not descendants of homo erectus however think of it like this:
during day time in Africa the weather is hot, thus predators like the big cats tend to limit their actions and keep in the shade(you will understand if you had a great deal of fare and hair on you)
humans(humanoids) being slower in motion and less muscular had better chance of survival if they could lose their hair, that is because less hair will mean more sweat area, means more thermal balance, means that they can move further and quicker during day time than their predators,
and thus loss of hair and more sweat glands will make them more able to survive, and thats why you are less hairy than a monekey
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hope i didn't get anything wrong, but cut me some slack I'm a computer guy
Topic: Some questions about evolution