Adding in a wider range of social-science expertise will not, in my view, help efforts to 'formalize the Anthropocene' as a geological age of human influence (E. Ellis et al. Nature 540, 192–193; 2016). The authors rightly want to expand the knowledge base involved in these efforts beyond stratigraphy and the Anthropocene Working Group, but their mistake is to assume that there can be agreed criteria — beyond 'golden spikes' and standard stratigraphic ages — that will allow new international bodies to determine how and when to make the epoch 'official'.

Social science shows that the way people perceive and react to environmental and social change is both varied and contingent. It can elucidate the value judgements in most things that people do, including by experts across all fields. Through research, we can determine why, how and to what degree human activity is changing our planet. But in my view, it is folly to believe that there is an objective way to define a new 'age of humans'.

What counts as epochal change is a matter of perspective and emerges from judgements about when quantitative change morphs into qualitative transformation. The interpretive and critical parts of social science can help us to appreciate that formalizing the Anthropocene is a misguided attempt to 'scientize' a particular set of value judgements. No such formalization is needed to underpin arguments for humans to live in ways that are less environmentally destructive.