The seven billion of us on the planet today share our world with the last remaining great apes. The chimpanzee, bonobo and gorilla in equatorial Africa, and the orangutan in Indonesia represent the last surviving tips of what was once a great lineage that dominated Earth's ecosystem for millions of years. But in the 21st century, they are in terrible trouble, in free fall toward extinction. It is highly possible that well before the century's end, one or more of the great ape species will hang on only in pathetically tiny numbers in protected wildlife sanctuaries.
The threats faced by great apes are many. They are hunted for meat in central and western Africa. Gorillas have died by the thousands in central Africa from outbreaks of ebola and other emerging viruses. Their forest homes are cut down to make way for farms, plantations and villages. In the west, there is a movement -- still debated in the United States -- to declare some basic form of human rights protection for the great apes, because they are genetically, psychologically and emotionally so much like us. Meanwhile, in their natural habitat they continue to decline.
Just as the early European settlers encountered indigenous peoples everywhere they went but nevertheless considered the frontier unoccupied, we wipe out ape habitat today because of a wanton disregard for the thin line separating apes from humans. Our DNA sequence similarity is well over 95 percent, their intelligence equals that of a human child, and their brains are more outsized to their bodies than any mammal other than ourselves. They and we share a common ancestor that lived six million years ago, a mere blip in evolutionary history.
The four great apes species are familiar to any zoo-goer. Chimpanzees are the best known, the subjects of long-term research in Africa beginning in 1960 with Jane Goodall. We are sister species, far more closely related to one another than chimpanzees are related to monkeys. A baby chimpanzee is born after a nearly nine month pregnancy, after which it is utterly dependent on its mother for several years. Even after being weaned from mother's milk, the death of a mother leaves an orphaned young chimpanzee emotionally traumatized. With good mothering, the juvenile chimpanzee reaches puberty at about age eleven, and if a female, she gives birth to her own first baby around age sixteen. In other words, the chimpanzee life cycle is not very different from our own, in keeping with our close evolutionary kinship. Perhaps the biggest difference between the life cycle of the female chimpanzee and a woman is that women experience menopause by age fifty, while the chimpanzee is often dead by that age.
Goodall's groundbreaking work was followed by long-term studies by other researchers, confirming our modern view of chimpanzees. They live in a complex fluid society called fission-fusion, which is perhaps an adaptation to a diet focused on widely scattered fruit trees, in which the only stable unit is a mother and her baby. Small parties of chimpanzees come together and split up as they travel through the forest all day long. Males tend to socialize among themselves far more than females do. Contrary to early assumptions that they were vegetarian, chimpanzees are omnivores that eat mainly fruit but relish the meat of small mammals, which they eagerly hunt. Males patrol their territorial borders with a vengeance, and attack and even kill males from neighboring communities.
The closely related bonobos are often known in the popular media as the "Make Love not War" apes, because of their very liberated and human-like sexual behavior. Unlike male-dominated chimpanzee society, female bonobos have found empowerment in alliances, forming coalitions that protect them from male coercion. Bonobos seem less interested in eating meat too. And the inter-community warfare that is a normal part of chimpanzee life has never been observed in wild bonobos. The sex life of the bonobo has come under scrutiny (and some media hype) for its apparent similarity to our own. Instead of sex for procreation only, which is the norm in the animal kingdom, bonobos also have sex for bonding, reconciliation, and to smooth over tensions among themselves. Sound familiar? Not only that, male and females copulate face to face, unlike chimpanzees, and same sex genital contact is common. Some of their ramped-up sexuality appears to be induced by the enforced proximity of captivity, as wild bonobos don't mate any more frequently than chimpanzees do. Bonobos are the most threatened of the African apes, numbering in the low thousands in their only habitat in the heart of central Africa. Civil wars and ongoing ethnic tensions have made accurate censusing of the last remaining populations inadequate, and at times impossible.
The gorilla is the largest living primate; a silverback male reaches an imposing four hundred pounds. For a century they were the misunderstood ape; considered savage and dangerous to African explorers who ventured into their forest realm. The reality has turned out to be much the opposite. Gorillas are peaceful, rather timid animals whose numbers have plummeted at the hands of humans who chop down their forests, shoot them for food, and spread transmissible diseases to them. Mountain gorillas, the species in eastern Africa made famous by Dian Fossey's work, number a mere 750 in two tiny forest fragments. In central and western Africa, lowland gorillas are more abundant but are also a major target of the bushmeat trade.
The only Asian great ape is the red-haired orangutan. The least social and also the least-studied of the apes, orangutans are in deep trouble. The Indonesian islands of Sumatra and Borneo are home to rapidly dwindling populations; the Sumatran orangutan population in particular is in freefall, now numbering only a few thousand. Indonesian rain forests are among the most wildlife-rich on Earth, but its government is firmly committed to converting nearly all of their forest resources to timber extraction and oil palm plantations. Orangutans reproduce very slowly; a female may only give birth once every seven or eight years, leaving the species unable to withstand the intense habitat loss it faces in the 21 century.
These four species, then, are your next of kin. As we destroy their forest homes, we extirpate not just gene pools but also indigenous cultures, for as we have learned in recent years, cultural traditions are defining qualities of the great apes. Chimpanzees are still used in some biomedical research, reduced to pincushions for drug-testing while imprisoned in tiny cages. In general, despite intense efforts to save the last great apes, many societies still regard them as commodities. Attitudes have changed, but it may be too late.
The survival of the great apes into the 22nd century is going to be determined by a host of factors, not the least of which is the engagement of the countries in which great apes live. The energy, expertise and money of western conservationists cannot save orangutans unless the Indonesian government takes action to prevent its last rain forests from being turned into chopsticks and lumber bound for China. In nations with little infrastructure and where political chaos reigns -- the Democratic Republic of Congo comes to mind -- the long-term prospects for the great apes are bleak. Conservationists have to hope for eventual political stability, an increase in human living standards and the improved wildlife conservation outlook that better human conditions bring.
Against all odds, the great apes have hung on in remote pockets of the world into the 21st century. Their fate will decided in the remainder of the century, as we grapple with large scale environmental changes that threaten our own lives as well. As is so often the case in environmental protection, their future is linked to our own. Only in a world that truly values their survival will they be a part of Earth's future biodiversity.