[aidenn0]

Before writing Clojure, Rich Hickey wrote FOIL[1], which used sockets to communicate between common lisp and the JVM (or CLR). When asked about making it in-process, Rich observed that the reflection overhead on the JVM was often as large, or larger, than the serialization overhead, so the gains to be had were limited.

1: http://foil.sourceforge.net/

[hinkley]

From what I recall, the Java team copped to the intentionally slow accusation, but that started to change when they decided to embrace the notion of other languages besides Java running on the JVM. Unfortunately that would have been shortly after Clojure was born. It took a few releases for them to really improve that situation, and that was still shortly before they started doing faster releases.