I think they are, Glen; I need to do some comparisons though.  It is indeed possible, I reckon, for voiceless ejectives to become voiced implosives in "lenis" or prenasalized environments.
 
~DaW~
----- Original Message -----
From: Glen Gordon
To: nostratic@yahoogroups.com
Sent: Wednesday, June 13, 2001 5:50 AM
Subject: [nostratic] A question on Proto-Afro-Asiatic



Danny Wier:
>Nilo-Saharan languages, however, have larger consonant inventories, >and
>Hausa and Chadic in general probably got its implosive voiced >stops from
>NS.

Why can't implosives simply be derived from earlier AA ejectives?

- gLeN