Believing that man should be guided by primitive instinct rather than reason, and determined to close the gulf between the species, Mr. Aspinall delighted in romping with his wild animals. He also encouraged his zookeepers to do likewise, sometimes with horrific consequences. Of his 30 best friends, he said, half were animals, and he argued that at one time there had been a golden age in which beasts and humans had been equal. Asked once whether he would leave his children in the company of his wild animals, he said, ''I'd rather leave them with gorillas than with a social worker.'' A tall, rangy man with a booming voice, Mr. Aspinall liked to shock the sedate and once announced that when having sex, he roared like a lion and beat his chest like a gorilla. His Darwinian beliefs led him to make admiring comments about the benefits of diseases like malaria to rid the world of inadequate human stock and cull it of two billion undesirables. He had no time for equality of the sexes, saying that his wife ''is the perfect example of the primate female, ready to serve the dominant male and make his life agreeable.''