 because we have historic records that we can look at that we can see the progression what his story well you're gonna run into problems with the pre-cambrian and cambrian period uh... which you may not be aware of that you should be if you want to do the science you know in in the cambridge period we had mostly maybe single-cell or multi-cell life and then all of a sudden bang over a very short geologic period of time all these different animals came into existence