Diet and feeding behaviour

The Hominidae family (also known as Great Apes) is the one that comprises Orangutans (Genus Pongo), Gorillas (Genus Gorilla), Chimpanzees and Bonobos (Genus Pan) and Humans (Genus Homo). A part from Humans, the other groups of the Hominidae family have similar patterns on feeding behaviours and diets. Orangutans, the more distant ones, base their diet in fruit (60%)[4]. It also includes insects, mineral rich-soil, some eggs, small invertebrates and young leaves and shoots. They spend one third of the day foraging for food. Gorilla’s diet depends on where is located (East or West in Africa); Eastern populations are folivorous (86%) while in Western populations fruits are the most important element. It has been seen in some studies that they also eat termites and animal-derived food[5]. Because of the poor nutritional quality of the food they have to eat a lot to meet their nutritional requirements, even then Gorillas use to sleep a lot not to lose energy. Chimpanzees and Bonobos (the closest non-human primate relatives to the Genus Homo) are quite similar but they differ that the latter are more sexually active besides the chimpanzees are larger.[6]Both are omnivorous. Chimps eat more insects and less fruit compared to bonobos. Termites are the most nutritionally important insects in their diet. Both species are opportunistic feeders and have social behaviour that lead them to share the prey from the hunting for the benefit of the population[6, 7].

As a conclusion from this part we can say that frugivory (feeding on vegetables and fruits) is central in primates diets. That´s why most of those animals are represented in the tropics, because there they can find the optimal resources for they needs while humans, concerning diet, have spread all over the world without constraint.

Figure 2. The hominin fossil record. Species are indicated with the dates of the earliest and latest fossil record. Adapted from Wood [8]

To get closer to humans we are going to quickly examine the feeding behaviour and diet patterns that our ancestors had. The first known hominid (proto-human) Ardipithecus ramidus (4,4M years ago) was omnivore, based on the enamel of the teeth, neither thick nor thin[2], suggesting an eclectic mix of foods without great dependence on ripe fruit [9]. This reconstruction of a generalized diet is supported by data from microwear analysis [9]. Three million years ago Australopithecus line diverged into sub-lines, one of those gave rise to Homo sapiens. Between 2.5 and 2 million years ago the climate changed a lot and this allowed the adaptive radiation of the species[10]. This, changed the landscape and also the food availability that put stress on many species to adapt to different conditions. This was the starting point of the human diet flexibility that was triggered to the ability to eat a big range of foods. This ability would have helped hominines to partition resources successfully in the face of competitors, and may have allowed them to move into new niches in novel environments more easily. Both (resource patronizing and rapid adaptation) are no more evident than in the Plio-Pleistocene [11]. Homo habilis -the first “true human”- who was able to use tools subsisted on wild plants and scavenging and/or hunting meat [12]. Meat became a more important part of the diet with its own contribution to the evolution of the specie. After, Homo erectus appeared (1,7M years ago) and it was the first human ancestor to control and use fire, another important tool that changed morphology and behaviour [13]. So on, 140.000 years ago the first anatomically modern human (Homo sapiens) appeared. It was at the same time of the last Ice Age. Thus implies harsh and rapid climatic changes and its feeding adaptations due to this fact. It may therefore be significant that fire came into widespread use around this same time corresponding with the advent of modern human beings. On the Late Palaeolithic (40.000 years ago) humans started processing some of their food with simple methods as pounding, grinding, scraping, roasting and baking [14].

Our nutritional requirements as humans are the result of the food interactions through the evolution from our ancestral species and the environment surrounding it. Our ancestors ate to meet their nutritional/caloric requirements, while today we continue eating for many different reasons, but specially to  gain euphoric feelings through the chemicals released in the body by the food we eat: the endorphins. This changes in the feeding behaviour and in the food we eat itself changed our bodies and is still changing. 

In the next section we are going to see some of those changes.