Talking Troubles?

Should I be worried that my 16 month old only consistently says two words ("bye" and "yeah")? I mean, he understands EVERYTHING. And he lets us know in his pointing, grunting, gesturing, excited way. He communicates, just not verbally. When we ask Max where something is (his cup, for instance), he'll run and find it. When I ask if he needs a new diaper, he runs over to the baby gate blocking the hall because he knows that means we're going in his room. He can point to body parts when you ask him to (he knows head, eyes, nose, tongue, ear, and foot) When I ask if he's ready for a bath, he gets really excited, climbs in my lap, and waves bye-bye to Chad. If I ask if he wants juice or milk, Max will run to the refrigerator and try to open it. And when he wants something, he points to it. When he wants to read, he brings me a book and climbs in my lap. When he wants to go outside, he runs to the back door and tries to open it. When we're at the park and he's ready to go home, he holds his arms up at me and starts saying "bye".

Also, the Max has this habit of saying a word for a few days and then never saying it again. He has done that with "outside", "duck", and "book." His first word was "dada." It meant "daddy" and "doggie." He eventually got around to saying "mama." He rarely says either of those now (although I do hear "mama" a lot when he's upset). There have also been several one-time-only words, including "ostrich", "cookie", and "paper."

I guess there's a wide range of "normal" when it comes to toddler behavior, but it just seems like the Max should be saying more actual words than he is (because he understands almost everything we say, yo). According to What to Expect: The Toddler Years I shouldn't be worried. It says that by 17 months a toddler should be able to use two words and may use as many as six. By 18 months toddlers will be using anywhere from 3 to 50 words. Holy crap! That's quite a range. Also, Max has already achieved most of the milestones listed in the 18 month chapter (point to a desired object, run, use a spoon/fork, point to 1 body part when asked - Max can already do 6, kick a ball forward, stack two blocks). He's barely 16 months old, and he's been doing most of those things for a couple of months now. I was just flipping through the book, looking at the milestones listed at the beginning of each chapter, and jumping isn't even listed until the 22nd month. I mean, Max (usually) holds onto something when he jumps, but jumping in the crib is one of his most favorite activities. I guess he's just focused on things other than talking right now.

But I can't help but worry sometimes. It's in my genes.