Lifespan and longevity are hallmark to the existence of species. Life history, which lifespan and longevity spawn from, is the basis for species to exist and a necessity for evolution to happen (Carey et al. 2001:411-412). With regards to the importance of paleodietary shift within the hominin lineage, it is imperative to understand that diet has had a lasting influence to longevity and lifespan within the genus Homo. Why do modern humans have such high life expectancies compared to their ancestors, and how has life expectancy changed within the genus Homo as its species has evolved? As time has passed, life expectancy within the genus Homo has increased due to numerous dietary advancements, such as the shift from heavy chewing to hunter-gathering …show more content…
To modern humans, it seems so farfetched that ancestral hominins ate such a remarkably different diet. Obviously, these changes observed in modern humans compared to ancient hominins happened on a macro-evolutionary scale over a span of hundreds of thousands of years. Morphologically speaking, diets based heavily, if not entirely, on low-quality plant material hold a correlative relationship between herbivory, low cranial capacity, and cranial robusticity. It is generally accepted that the cranial capacity of early Homo was around 500-650cc. Homo habilis is considered the first species within the genus Homo, and it lived from 1.8-2.5 m.y.a (Cela-Conde et al. 2007:159-162). It was marked by increased use of material culture, an australopithecine-like body, and it was the first hominin species to eat a diet based heavily on animal protein. Classically, H. habilis stone tool use and animal protein consumption has been attributed to scavenging of animal carcasses left behind from predatory animals higher up in the food chain. However, the proximity of H. habilis fossils to Lake Turkana suggests that stone tool use could have been used to gain access to ¬¬freshwater animal protein sources (Braun et al. 2010). Consumption of these freshwater animal protein sources, such as fish, could have provided important nutrients to provide an evolutionary pathway for increased cranial capacity seen in later Homo species (Braun et al. 2010). Ultimately, the diet of H. habilis was limited due to its australopithecine-like morphology, which made it difficult for H. habilis to physically go after any animal that moved at fast speeds or defend itself from larger predatory animals that it competed with. Much like its Australopithecine ancestors, H. habilis relied on gathering to collect its meals. Lifespan for H. habilis is interesting in the fact that