[gus_massa]

Mutations are random, but to get a new "feature" you need many small mutations in the right direction. To accumulate the useful mutations you usually need that the intermediate mutations have some are useful alone. Most of the time these mutations have a side cost, so if the intermediate steps are not useful they are "discarded" because the non mutated members of the population outnumber the mutated population.

I think that most of us understand more about ostrich than about virus. Let's make a think experiment. How difficult is that ostrich become airborne? How many mutation they need? Is it possible? Is it dangerous?

I hope there is an ornithologist nearby, but I'll try:

* Stronger chest muscles

* More white meat in the chest muscles

* Longer wings

* Better feathers

* Lighter bones

* Shorter and lighter legs, to reduce weight

* Less brain? (less weight)

* Do you need some special brain areas to fly?

Ostrich is a case of neoteny ( http://en.wikipedia.org/wiki/Neoteny ), so many features can be possible changed at one. But it's a old case, so the genes for the features needed to fly are probably partially overwritten with garbage since a long time.

[mhewett]

This is irrelevant. To be transmitted via an airborne vector does not require Ebola to mutate into a flying virus.