HFT = electronic trading, or at least the bulk of it. The human traders that existed before HFT firms & HFT desks at banks were largely doing the same thing that HFT firms do now - making markets on a wide range of securities, but less efficiently.

Latency-arb is a small part of HFT, if you consider strategies that provide liquidity to be "good HFT" and strategies that take liquidity (via latency arb or other arbs) to be "bad HFT" then those strategies are largely executed by the same market participants.