Questions? AskAuckland


What is Human Evolution?

This page supports specialist and non-specialist teachers by providing background information about the concepts that underpin the LENScience resources on human evolution.

The Evolution of Humans


Human evolution is the process by which over time, humans have changed to optimise the fit between the individual members of a population and their environment. In contrast to the modern human desire to live a long life, evolution is directed primarily by the biological drive to reproduce and pass genes on to successive generations. Only lineages that can successfully reproduce will survive.   


The process of evolution is driven by the interaction of humans with their environment. The sum of the interactions between the individual and all biotic and abiotic components of their environment will determine the success of the individual in passing on genes and therefore contributing to the survival of the population and features of future generations. These interactions are vast and complex. They present significant variables, including the complexity of intra and inter‐specific interactions playing out in response to biotic and abiotic factors which, when combined with the variation present within the individuals within the population, determine survival.


In biological terms, humans sit with the great apes within the hominoid group but are distinguished within this group by specific physical and behavioural traits including bipedalism, brain size, hairlessness, tool making, language development, abstract thought, social organisation and culture. Current molecular evidence suggests that the pathway to modern humans can be traced back along the hominoid lineage with the first split being the Orang‐utan lineage around 15 million years ago, with the last branch that leads to Homo sapiens splitting from apes 5‐6 million years ago (Fig 1). These dates are based on evidence from the molecular clock which assumes a consistent rate of mutational change over time. 


The evolution of Hominins (humans and their direct ancestors) has been noted for the development of large brains (leading to intelligence) and relatively long lives. Bipedalism is one of several factors selected for that have resulted collectively in the development of intelligence and the success of the hominins. However, the adaptive advantages that these selected features bring are accompanied by adaptive costs. Collectively, adaptive advantage must outweigh adaptive cost for the evolutionary success of the species. However, evolutionary fitness (and the adaptations selected) does not necessarily match health and longevity.

Evolutionary Fitness

The concept of fitness is central to understanding evolution. Evolutionary fitness is a measure of the match between an individual and its environment to best enable successful reproduction. It is important to note that fitness is measured as the ability to reproduce and live long enough to support offspring to the point where they reach reproductive age. Selection is based on adaptations that contribute to the success of reproduction. Health and longevity beyond reproductive years are not generally drivers in evolutionary selection processes.


Adaptive Radiation

Adaptive radiation is an evolutionary pattern whereby (relatively) rapid diversification within a lineage can be traced from a common ancestral origin, resulting in the existence of multiple related genera and species which have evolved to occupy multiple niches present within an environment. Both the primates and the hominins display this pattern of evolutionary development. While exact relationships continue to be debated within the hominin group, it is clear that this group existed from around six million years ago, and included multiple related species, some of which may have co‐existed (Fig 2). 



Adaptive radiation leading to speciation is driven either by species entering new ecosystems, or changes in environment which create different selection pressures and therefore the potential to alter the phenotype that is selected for and survives. Each species thrives in a niche for which it is best adapted, with divergence reducing competition between species. It is likely that the adaptive radiation seen in the hominins species was driven by environmental change, perhaps reflecting climate change.