How did humans come to be everywhere?

That doesn’t surprise us – but it should. Most species are not so globally distributed. Indeed, some are found only on a single island. My research explores how humans came to be a terrestrially pervasive species, found on every continent and in virtually every type of ecosystem.

Crucial to our global dispersal have been a number of traits:

• the ability to adapt to novel and changing environments,
• the ability to form strong social bonds, and
• our capacity for advanced technological and symbolic behaviour.

These and other critical human traits have emerged through time, and enabled an unprecedented global expansion.

What cultural adaptations made us niche constructors?

We are adapted to neither extreme cold nor extreme aridity. Yet, as a species, we have spread across deserts and oceans, up mountain passes, and into some of the most extreme and inhospitable environments on the planet. And we have not only found these places, but flourished in them, establishing towns, cities, even empires.

We did so by creating with culture what we lacked in biology. Our material culture has allowed us to thrive, and to shape the world to our needs. We have created complex tools, elaborate trading networks, and diversified agricultural systems, and harnessed other species for our needs. This is the human niche.

Culture has allowed us to survive at least one volcanic super-eruption and various climatic challenges, as well as to adapt to rising sea levels. It has also enabled major population expansions – the emergence of dairying culture, for example, allowed early pastoralists to expand across the Eurasian steppe and Mongolia, into the arid interior of eastern Africa, and up into the stark, cold interior of the Tibetan highlands. Early globalization transported plants and animals to new environments, enriched food and ritual traditions, and facilitated extraordinary migrations, including the ancient colonization of Madagascar by Southeast Asian populations thousands of kilometers across the ocean.

How have humans shaped the biosphere?

While present-day climate warming is the most substantial and potentially destructive way that humans have transformed Earths’ environments, it is increasingly clear that our species has been altering global ecosystems for many thousands of years. By the Late Pleistocene (∼129,000-11,700 years ago), as our species spread rapidly into new habitats and continents, humans had the technological proficiency to significantly alter and shape their environments. While much of this environmental transformation was likely sustainable, and supported diverse kinds of biodiversity, early humans may also at times have had more destructive impacts. For example, many archaeologists link the expansion of Homo sapiens to a series of large-scale extinctions that eliminated many of the Earth’s biggest animals, including other human species like Neanderthals.

As our species subsequently developed ever more sophisticated cultural and technological capabilities, we increased our ecological footprint. This was done by introducing species into new areas, gradually replacing wild with human-domesticated and commensal species, altering biodiversity, nutrient flows and species composition, and driving many plants and animals to extinction. By 3000 years ago, early hunter-gatherers, farmers and pastoralists had already transformed much of the Earth’s land through a variety of intensive and extensive uses. Subsequent European colonialism deepened these impacts through exploitive and extractive systems that intensified species loss and species invasions, and significantly expanded the land under agricultural production.

These early, pervasive and widespread human impacts have led to calls to place the start of the Anthropocene – the era of large-scale human transformation of Earth systems – in the prehistoric era. Many archaeologists, palaeoecologists and palaeobiologists see the start of the Anthropocene not as a moment in time, but as a gradual accumulation of impacts from a surprisingly early date.

How is the past relevant today?

Archaeology today is dramatically different from the privileged gentlemen’s pursuit of the past, or from the treasure-hunting often depicted on screen. As the discipline moves beyond its colonial and nationalist roots to become a modern science, its relevance to present-day challenges becomes increasingly apparent. Contemporary archaeology bridges the humanities and sciences, and provides useful information on long-term biodiversity change, climate impacts, and ecological violence under colonialism, for example. It can also help support conservation and restoration agendas.

Looking to the past also helps us see that some societies have contributed in critical ways to creating the biodiversity we value today. For example, many Indigenous groups undertake traditional land management practices that help to maintain and protect biodiversity. The deep time dimension of archaeology and related disciplines like palaeontology and palaeoecology provides much needed context that helps support understanding of the long-term relationships between people and places, promoting efforts towards ecological and climate justice.