500 out of how many?
Ping.
500 is a pretty large number "going against the grain"
There's what - 6,000,000 or so scientists in the US?
500 / 6,000,000 = 0.0083%
OK, now only 99.9% of scientists believe in evolution.
Who cares "out of how many"? Since the consensus always seems to be that "virtually all scientists agree with evolution as Darwin envisioned it", any number is huge and 500 willing to sign a paper is even more significant. The more pertinent question might be, "How many more feel this way, but declined to sign the paper?"