Excerpt from Unlocking the Mysteries of Creation, by Dennis Peterson. 

When you see an 18-foot high crane-like giraffe, you can't help watching that amazing neck as it bobs up and down.  The giraffe has one of the largest hearts in the animal world and nearly double the blood pressure of any creature.  When you consider what a stretch uphill it is to pump the blood to his head, you can see why there's a problem.   But what seems like a problem has a marvelous hidden solution.  The jugular blood vessels in the neck have a series of one-way check valves to hold back the blood from rushing to the brain when it lowers its head, and to prevent it from flowing away from the brain too quickly when it lifts its head again.  As a additional protection, a network of spongy tissue at the base of the brain soaks up any excess blood.  Could you call this an amazing demonstration of plumbing technology?  How important do you think this technology is to the giraffe?

Now, you know how it is when you have been bending down low and then suddenly stand and lift your head up.  You get a little dizzy, don't you?  Think of the giraffe, Can you imagine those valves not working perfectly at any supposed evolutionary state?   The first time he bent down for a drink of water the poor giraffe would literally blast his brains out from all that blood bearing down on his head.  The simple act of raising his head up from a nap would result in such a loss of blood from the brain that he would pass out and be easy prey for a nearby lioness.

One of Darwin's silliest ideas in his book, The Origin of Species, was that during a long drought, some imaginary pre-giraffe that was taller than others could reach the scarce leaves upon which it fed.  These survivors supposedly "left offspring inheriting the same bodily peculiarities, while individuals less favored in the same respects would have been the most likely to perish."  And thus Darwin concluded, "by this process long continued, an ordinary hoofed quadruped might be converted into a giraffe."

You can't help wondering how the baby giraffes managed to survive during this incredibly long drought!  Of course sensible scientists now know that acquired characteristics cannot be passed on to offspring.  Furthermore, no fossil evidence supports the idea.  Giraffes have always been giraffes, plumbing and all.