MPRG Naturalistic Social Cognition
(Concluding Report)
Head: Annie E. Wertz
Introduction
The Max Planck Research Group Naturalistic Social Cognition explored social learning and cognitive development from an evolutionary perspective, with a focus on infancy and early childhood. The group’s primary research program investigated how infants and young children learn about plants. The group used a combination of laboratory studies, naturalistic observations, cross-cultural studies, and cross-species comparisons to examine this previously unexplored aspect of the human mind. The group's work established a novel area of inquiry within the field of cognitive development. This group started its work in 2015 and concluded in 2023.
At first glance, it may not seem like plants would play a major role in shaping the human mind. The kinds of environments in which many of us spend our time give the distinct impression that plants are a very small part of human life. Imagine your home, your office, your city, or hometown. In what contexts do you encounter plants? Perhaps you picture houseplants in pots, or fruits and vegetables piled on shelves in the supermarket, or grassy lawns and tree-lined gardens. In these kinds of environments, plants can be an afterthought, or at least a part of our lives we do not have to think about very much. But shifting our frame of reference a bit shows just how mistaken this impression is (Figure 1).
Left image: 12019 on Pixabay, CC0
Right image: Thomas Wolter on Pixabay, CC0
In fact, life is mostly plants. Recent estimates indicate that about 80% of the biomass on Earth is plants. The sheer ubiquity of this form of life means that plants have likely played a significant role in the evolution of most organisms, including humans. Of course, in order to impact human evolution, plants must have been a consistent feature of human ancestral environments, and here we are on fairly firm ground. Contrary to claims that one cannot know anything about ancestral environments, we can be reasonably confident that plants were present throughout human evolution. The first vascular land plants appeared around 450 million years ago and the first scale trees and seed ferns emerged about 350 million years ago, well before the first dinosaurs and mammals. The first flowering plants appeared around 180 to 145 million years ago, well before the first primates emerged around 65 to 56 million years ago and made their living in the trees.
Humans evolved in a world replete with plant life and there is good evidence for a long evolutionary history of plant use, extending well back to our hominin ancestors. The evidence shows that our ancestors had plant-rich diets and provides clues to the types of plants on which different hominin species relied. The picture is complex, but in general terms, the genus Homo had a relatively broad-based diet compared to earlier hominins and tended not to specialize in one type of plant resource. Analyses of plant micro-remains from dental calculi and stone tool residues from Neanderthals and early modern humans underscores the breadth of plant resources that were exploited. The results suggest that both species consumed a wide array of plant foods, including grass seeds and underground storage organs such as tubers and bulbs.
It is also extremely well established that plants have shaped countless adaptations in other animals and vice versa. The breadth and variety of these adaptations is beyond the scope of this section of the report, but a few well-known examples are the differently shaped beaks of Darwin’s finches and the camouflage of the leaf insect (Figure 2). Plants have also shaped cognitive adaptations in animals. For example, several species have been shown to categorize different types of plants based on predictive features. Bees who learn to forage at one type of (artificial) flower generalize this information via the color, pattern, and scent of the flowers. Similarly, sheep distinguish different plants based on invariant features of plant species like leaf shape, not variable features such as height.
Figure 2. Some adaptations shaped by plants. The beaks of Darwin’s finches (left panel) are well tailored to the food sources the birds exploited on different islands in the Galapagos. For example, one type of finch fed on hard plant seeds and had a correspondingly shorter and more powerful beak, while another fed on insects plucked from bark and other vegetation and had a much thinner pointed beak. Leaf insects (e.g., Pulchriphyllium pulchrifolium, right panel) evolved features to mimic their densely leafy habitats and camouflage themselves from predators.
Left image: from Birds. The zoology of the voyage of H.M.S. Beagle by John Gould, 1841; public domain , the author died in 1881, copyright in country of origin and others have expired
Right image: “Pulchriphyllium pulchrifolium, Pärchen” by Drägü on Wikimedia, CC BY-SA 4.0
Therefore, the claim that plants have shaped the human mind should be uncontroversial. And, in fact, it is a claim that has been made by others to account for specific aspects of human behavior. For example, young children’s tendency to reject eating vegetables has been hypothesized to be a mechanism for avoiding accidental plant poisoning. However, to our knowledge, there was no systematic study of the ways in which plants have shaped the human mind prior to the work of the MPRG Naturalistic Social Cognition.