4MB are enough to discriminate between 2^(3.2 * 10^7) possible states. Suppose you have a decompressor that can interpret a percent of a percent of a percent of a percent of those states as functional lifeforms. There are about a trillion species on the planet[1]; let's say there are a trillion times as many potential species that don't currently exist and a trillion variations within each. And then let's multiply by another trillion for good measure. Wolfram Alpha tells me[2] we've left a margin of error of roughly* ten to the ten million.
Even a SHA-256 hash would leave 10^31 margin of error. The "percent of a percent of a percent of a percent" part is sweeping a lot under the proverbial rug here ;)
[1]https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446
[2]https://www.wolframalpha.com/input?i2d=true&i=Divide%5BPower...
*'roughly' in the sense that a mountain range is roughly coarse sandpaper, but too round not to round to