Could Chimps and Humans Mate? Tales of 'Humanzee' Hybrid Are Murky and Likely Impossible

Tales of a "humanzee," or chimp-human hybrid, are as common as they are compelling. But to say nothing of whether or not such a hybrid could be possible, all signs point to the tales being fabricated.

An old rumor has circulated in headlines again, that a scientist has claimed a humanzee once existed. The Sun reported that evolutionary psychologist Gordon Gallup had recalled an alleged experiment in which scientists impregnated a female chimp with human sperm. According to the story, the chimp gave birth to a hybrid, but the scientists became concerned with the ethical implications the infant would bring up, so they allegedly killed it.

Gallup doesn't claim to have witnessed the experiment, but The Sun reports that another professor, whom he trusted, told him it was true. The story gets murky and inconsistent as it passes from person to person and as time goes on.

Science Alert explains that, although the experiment is purported to have occurred at the Yerkes National Primate Research Center in the 1920's, the center hadn't even been called that until the 30's. ScienceAlert reports that the facility went by the names Yale Laboratories of Primate Biology and Anthropoid Breeding and Experiment Station. Furthermore, the idea of killing a half-human child for ethical reasons seems counterintuitive.

However, there have been multiple, documented attempts to breed humans with chimpanzees, who, along with bonobos, are our closest relatives. For example, in the 1920's, Soviet scientist Ilya Ivanovich Ivanov wanted to make a "chuman" by impregnating women with chimp sperm while pretending to conduct a medical exam, according to New Scientist. The experiments were to take place in Guinea, which was a French colony at the time. The French governor forbade it, and although Ivanov later found willing volunteers in the Soviet Union, his sperm-donor chimp died before he could proceed.

The Chicago Tribune reported in 1981 that a scientist had claimed to have successfully impregnated a chimp with human sperm in 1967. But the experiment was interrupted when the laboratory was smashed by authorities under the Chinese Cultural Revolution and the chimp reportedly died from neglect.

There isn't a scientific consensus over whether such a hybrid is possible. Humans and chimps have DNA that is 95 percent similar, and 99 percent of our DNA coding sequences are the same as well. However, humans have 23 pairs of chromosomes in our DNA, while chimps only have 22. The difference makes bearing healthy young difficult, and the offspring would be infertile. Furthermore, often, differences between the physiology of separate species, even when they're similar, may make interspecies-hybridization impossible.

Hybridization is fairly common in the animal kingdom. It can lead to new species very quickly, as in the case of a new species of finch, as well as "coywolves" and "grolar bears." However, as compelling as it is to see a half-zebra, half-donkey, the concept of a "humanzee" is particularly intriguing because of its potential existential impact. If a half-human, half-chimpanzee could be created, would it have human rights? And how might it fit into larger society?

Fortunately, we may never have to answer those questions.