Lockjaw is a dog.
Pretending that he is a person was a Joke they played on the Thing.
Ben thinks that Lockjaw is a stuck up dick who keeps snubbing him, and everyone else is laughing their ass off behind the Thing's massive brickhouse of a back.
From wikipedia...
At one point, Quicksilver and the Thing witnessed what appeared to be Lockjaw, apparently a sentient being once mutated by Terrigen Mists, speaking to them. This convinces Quicksilver not to expose his daughter Luna to the Mists.[10] However, Lockjaw later brought Quicksilver to Washington, D.C., in search of X-Factor, and Quicksilver there stated that Lockjaw's sentience was actually a hoax perpetrated on the Thing by Karnak and Gorgon.[11]
Comicvine says he was an inhuman child that became a dog because of terrigenesis, and the marvel wiki says he gained his abilities through terrigenesis as a child, and it would be kind of weird for an animal to have Inhuman DNA and go through terrigenesis.
Also, from Marvel.com
http://marvel.com/universe/Lockjaw
So, marvel's official site says he was mutated into the dog form, from a normal inhuman. The link does have "contributors", but it looks like Marvel's character stuff isn't just something any random person can edit. Karnak and Gorgon may have faked him speaking one time, but I'm staying with him being a humanoid as a child (which makes more sense than giving a puppy super powers) based off of it being said on Marvel's site, along with the whole puppy terrigenesis thing making no sense.Lockjaw is a member of the Inhumans royal family, mutated by the Terrigen Mists into his canine form.
Then how do you explain this?
http://marvel.wikia.com/Puppy_(Earth-616)
Hmmm?
The page in question...

The official website can suck it. Marvel's official website is not canon and more so seeding conjecture as fact is only going to trick future writers into believing bosh. below is a lengthy fair and balanced argument, taking into account both sides and a lot more additional facts from canon, and really decides in the end that the call is too close to make.
http://zak-site.com/Great-American-Novel/lockjaw_talks.html
The Inhumans keep slaves (Alpha Primatives) why wouldn't they want super powered beast of burden to support their infrastructure and economy?