The giraffe needs an extremely powerful heart pump to get blood through its long neck and into the brain to counter gravity's pull down.  But what happens when the giraffe bends down to drink water?  Its heart should blast blood down the neck so fast that it would destroy the brain.  Instead, when the giraffe bends down, separate blood vessels let the blood down slowly where it hits a soft sponge that protects the brain.  How could this complex system have evolved slowly?