Does Homo ergaster disprove early speech development?

[JTEM]

Someone threw a monkey wrench on the gears of
paleoanthropology: Homo ergaster.

Everyone seems pretty confident that ergaster
lacked the physical capacity for genuine speech.
To quote one story:

: The vertebral canal of Nariokotome Boy does not
: seem developed enough to have given him the
: control over his breathing needed for complex speech.
http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/leaving_home1.shtml

...but at the same time, Homo habilis is believed
to have stretched back even further (habilis is
supposed to be older), and most seem pretty
confident that habilis *Did* have speech:

: The bulge of Broca's area, essential for speech, is
: visible in one H. habilis brain cast, indicating that
: the species may have been capable of rudimentary
: speech.

http://www.pbs.org/wgbh/evolution/humans/humankind/j.html

Now I don't have any problems balancing the two, and I
don't have to sweep one of them under the rug as an
"Evolutionary dead end," a cousin on the family tree. Nope.
We're dealing with separate populations here, each
adapting to it's own unique environment.

Anyone care to venture an explanation?

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