NEXT OF KIN: What Chimpanzees Have Taught Me About Who We Are.<i> By Roger Fouts with Stephen Tukel Mills</i> .<i> A Living Planet Book/William Morrow: 420 pp., $25</i>

Cogito, ergo sum may sound harmless enough, but in the wrong hands, Descartes’ maxim can be devastating. Humans have minds, it says, whereas other animals merely have bodies. Cartesian dualism allows us to suck the air out of a space capsule to see how long it takes an oxygen-deprived chimpanzee to die, isolate infant chimpanzees in cages for years to see the effects of maternal deprivation or give them polio or hepatitis or HIV. They’re just animals, after all. And even for people revolted by such experiments, there’s a lingering dualism that gratefully takes the chance of discovering benefits for humans in exchange for the cruelties taking place behind laboratory walls.

The triumphant story of Washoe, the chimpanzee heroine of “Next of Kin,” challenges all that. How she started her journey from West Africa’s forests to a world of fame is unknown, but if standard procedures were followed, she was probably clinging to her mother’s breast when dogs chased them up a tree. Her mother was shot to death, and the baby fell with her. She would then have been carried in a basket for several days to an animal dealer who supplied the U.S. Air Force with infant space cadets. In 1966 at the Holloman Aeromedical Laboratory in New Mexico, Washoe escaped aeronautic experiments by being chosen as the first ape to be taught American sign language. The graduate student assigned to her was Roger Fouts, who served Washoe as a nurse as well as a scientist. Now, 30 years and three homes later, Washoe and the author are still together. No two minds of different species have come to know each other better.

“Next of Kin” melds Washoe’s story and the results of other chimpanzee language studies into an enthralling conjecture about what ape intelligence can tell us about the evolution of the human mind. The book considers human brain asymmetry, autism and the nature of language. It includes a persuasive scenario about how human language is built on cognitive abilities thought to have been possessed by our ancestors from 5 million years ago and evidenced today by chimpanzees. The book is also an autobiography that portrays Fouts’ uneasy intertwining of personal and professional conflicts, enlivened by anecdotes about a Frankenstein-like director of the Institute for Primate Studies in Oklahoma and stories about alcoholic escapes into the wilds of Oklahoma.

But “Next of Kin” is more than a book about the theory and practice of science. It’s a love story. Fouts was a California farm boy with ordinary training in psychology and no particular interest in animals until he was introduced to Washoe. “Although my first dog had been a wonderful companion, she had never evoked the deep and tangled emotions of friendship, competitiveness, anger and love that I felt for this baby chimpanzee,” Fouts writes. “When I played with Washoe I felt like I was with one of my brothers again, wrestling with an equal who could give as good as he got, both physically and psychologically. Quite often I had to remind myself that this little chimpanzee girl was not a human being. But after a while I realized this distinction had become meaningless to me.”

This is dangerously honest talk which certainly won’t help bridge the yawning gap between those who accept ape-language studies and those who dismiss their relevance to human cognition. Scientists aren’t supposed to have their objectivity ruined by emotional involvement. But “Next of Kin” shows that the ape experiments that fail are those that forbid human sympathy for their subjects. For Fouts, chimpanzee and human minds are fundamentally alike, so it makes sense to care deeply about one’s chimpanzee subjects.

Fouts recalls many instances reminiscent of human behavior. There were adult males who escaped from their colony by twisting the chain-like fence but would never do it if they were being watched. There was a chimpanzee named Lucy teaching her kitten to use the toilet by dangling her over it, waiting, then flushing. There was a time when Washoe refused to step on a doormat until she had tested it by putting a doll on it first. The argument for mental similarity, based purely on such observations, is persuasive. But the ape-human connection becomes especially striking when direct communication with the subjects is possible. Take Washoe’s interaction with Kat, for example. Kat was a volunteer who came to work every day with Washoe when the chimpanzee was 17 years old. When Kat became pregnant, Washoe was fascinated. Washoe had had two pregnancies of her own (both ending in early death), and she paid regular attention to Kat’s belly and the baby inside. Using sign language, she would ask about the baby. Then, without warning, Kat stopped coming to see Washoe. When Kat returned, Washoe greeted her warmly but became unusually distant toward her. It seemed as if Washoe had been hurt by Kat’s absence. Kat told Washoe why she had stopped coming. She had miscarried. “My baby died,” Kat signed. Washoe looked down, then at Kat and signed “cry.” “Please person hug,” she signed later, when Kat had to go.

Such interactions in “Next of Kin” light up the accounts of chimpanzees like Washoe, Lucy, Ally, Loulis and Booee and highlight the importance of emotion and bonding in the language experiments. By the time we read about Washoe signing Ally’s name when meeting him after four years of separation, we realize that it’s their special friendship that makes Washoe want to sign. When Washoe took a chair to her 1-year-old son and tutored him by signing “chair sit,” it’s because she cared about what he did. When Fouts persuaded Washoe to stay indoors by telling her that “big black dog out there eats little chimpanzees,” which caused Washoe to retreat to the farthest corner and sign “no no dog,” it becomes clear that it was possible only because of the special trust between them. Fouts argues convincingly that all communication, whether between humans or chimpanzees, requires an emotional component beyond the simple manipulation of symbols.

Skeptics worry that students of ape signing over-interpret their observations. Fouts shows that some of these concerns are unfounded. For example, the idea that apes have been given rewards to use sign language has been proved wrong, most dramatically by Washoe’s adopted son Loulis, who learned signing from her without human participation. But when Lucy signed “cry hurt food” after eating a radish for example, was she naming the radish, or merely giving three different responses to the sensation of eating it? After all, she used this combination only once. Fouts says that chimpanzees can invent two- or three-word names, but the case doesn’t look settled yet.

In “Next of Kin” Fouts presents much of the evidence that suggests that chimpanzee signing is a linguistic skill, and he responds to some of the challenges of the evidence, elegantly explaining why he thinks human linguistic abilities go back to our ape origins. But he steps aside from a full confrontation with the naysayers because he has more important things to do.

During the long search for a permanent home for Washoe (which they eventually find at Central Washington University in Ellensburg, Wash.), Fouts begins to feel outraged about the treatment of chimpanzees used for science. He witnesses chimpanzees kept in tiny cages, living alone, poorly cared for or subjected to needless and cruel experiments. He is troubled by the nagging reminders that chimpanzees can live for more than 60 years and that the United States still has hundreds of chimpanzees that were recruited for the space program and aren’t needed anymore.

By the time we learn about how poorly chimpanzees are treated (often in disregard of federal regulations), the issue of the degree of their linguistic skill becomes less important than the fact that each one needs looking after. Lucy, who signed on the cover of Life magazine in 1972, was released into the wild and killed by unidentified people in 1988. Ally was returned to the biomedical world and is apparently part of a toxin testing program in New Mexico. Booee spent years in a tiny cage and was injected with hepatitis C. The lucky ones, like Washoe, have one thing in common; they have someone who cared.

What Fouts has learned from chimpanzees is that Descartes was wrong. Other animals do have minds. The reason chimpanzees are chosen for experiments is that they are so like us; our compassion should be greater. That argument isn’t new, but in “Next of Kin,” it is based on an unparalleled depth of understanding and on a uniquely personal involvement in the battles over congressional legislation and laboratory management. You cannot read this book and stay neutral.