An image captures elephants, or megaherbivores, in Tarangire National Park, Tanzania, Africa. These large creatures were once far more diverse and numerous than they are now. Photo credits: Juan Cantalapiedra.
Faysal Bibi, affiliated with Berlin’s Museum für Naturkunde, and Juan L. Cantalapiedra of the University of Alcalá, Madrid, made extensive use of fossil teeth measurements to trace the size and population dynamics of large African mammals (weighing more than 15 kg or 33 lbs) over the past 10 million years.
Even considering the inherent difficulties with fossil record preservation, the research revealed a consistent relationship between an animal’s size and its population density in both ancient and modern communities. This points to the continuation of core ecological processes that shape our current living communities being discernible in the fossil record.
The researchers found that for animals heavier than 45 kg, an increase in size corresponded to a decrease in population density, aligning with the ecological ‘rule of metabolic scaling’. According to this rule, larger species have sparser population densities than smaller ones. An unexpected deviation from this pattern was that mammals weighing between ~15 kg (33 lbs) and 45 kg (99 lbs) were much less common than predicted in both current and fossilized communities. This finding was seen as indicative of savanna environments where monkeys and small forest-dwelling antelopes are sparse.
The researchers made a surprising discovery while studying how size-abundance distributions evolved over time. They found that communities older than ~4 million years had a significantly higher number of large animals and a larger percentage of total biomass in the larger size categories than younger communities.
The abundance of large individuals in these ancient African communities — including some elephants weighing more than 10 tons — is unmatched in today’s ecosystems. A gradual disappearance of large individuals from the fossil record has been noted since that time, signifying a long-term drop in the diversity of large mammals from the late Pliocene and Pleistocene, leading to the ‘downsized’ communities we observe today.
The study supports recent theories suggesting that African megafaunal losses date back to ancient times, questioning the belief that the downfall of African megafauna was mainly due to human activities.
While human expansion worldwide during the late Pleistocene and Holocene (the last ~100,000 years) coincided with a massive extinction of many large animals, the research endorses the notion that megafaunal losses in Africa started around 4 million years ago, well before humans developed efficient hunting skills. The study spotlights environmental changes, such as a long-term drop in global temperatures and the expansion of tropical grasslands, as potential catalysts for megafaunal extinctions.
The study also suggests that the loss of larger creatures and the reshaping of biomass distribution in African large mammal communities might have been related to a drop in primary productivity. Using a known correlation between mammalian tooth shapes (morphological traits) and plant productivity (net primary productivity) today, the researchers estimated past productivity levels for African communities.
Their calculations showed an approximately two-thirds decrease in productivity since the Late Miocene (> 5 million years ago), a trend witnessed worldwide, which could have drastically reduced the carrying capacity of large mammal communities, leading to decreased diversity and sped-up extinction of large species.
This research opens up new pathways for understanding the dynamics of ecosystems and the intricate interplay between individuals, species, and their environment. Through the analysis of fossil abundance data and the incorporation of size-based methods, scientists can glean valuable insights into the ecological factors driving extinction.
The publication of this study represents a significant step forward in our comprehension of African megafaunal extinctions and the reformation of ecosystems over geologic timescales. The findings of Bibi and Cantalapiedra have the potential to guide conservation strategies and improve our capacity to anticipate and manage the impacts of biodiversity loss amidst environmental shifts.
Reference: “Plio-Pleistocene African megaherbivore losses associated with community biomass restructuring” by Faysal Bibi and Juan L. Cantalapiedra, 8 June 2023, Science.
DOI: 10.1126/science.add8366
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Frequently Asked Questions (FAQs) about African Megafauna Decline
What is the main focus of the research conducted by Faysal Bibi and Juan L. Cantalapiedra?
The primary focus of the research by Faysal Bibi and Juan L. Cantalapiedra is to investigate the decline of large African mammals or ‘megafauna’ over the past 10 million years using fossil teeth measurements.
What significant pattern did the researchers observe in relation to an animal’s size and population density?
The researchers observed that there was a consistent correlation between an animal’s size and its population density in both ancient and modern communities. This means larger species tend to have lower population densities compared to smaller ones.
What unique discovery did the researchers make regarding size-abundance distributions over time?
The researchers discovered that communities older than ~4 million years had a significantly higher number of large animals and a larger percentage of total biomass in the larger size categories than younger communities.
What challenges the idea that the decline of African megafauna was primarily driven by human activities?
The research suggests that megafaunal losses in Africa started around 4 million years ago, well before humans developed efficient hunting skills. Environmental changes, such as a long-term drop in global temperatures and the expansion of tropical grasslands, are highlighted as potential causes for these extinctions.
How does this research impact our understanding of biodiversity loss?
This research opens new pathways for understanding the dynamics of ecosystems and the complex interplay between individuals, species, and their environment. The findings could guide conservation strategies and improve our capacity to anticipate and manage the impacts of biodiversity loss amidst environmental shifts.
More about African Megafauna Decline
- Faysal Bibi’s profile at Museum für Naturkunde
- Juan L. Cantalapiedra’s profile at University of Alcalá
- Tarangire National Park
- Science Journal Publication
- Megafauna Extinction
- Rule of Metabolic Scaling
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6 comments
Amazing to think that there were so many more large animals in Africa 4 million years ago, we’ve certainly lost a lot, sad really 🙁
10 million years of history in fossil teeth, wow! thas some deep time detective work right there, kudos to the researchers!
it’s sad how much biodiversity we’ve lost over the millennia… we need to do better for our planet.
hey this is some cool stuff, kinda wish i cud see those 10 ton elephants in real life lol. great research, love this kinda thing!
Fascinating! never knew that the animal’s size is linked with its population density, makes sense though, big creatures need more resources to survive.
Incredible research! Its really adds a lot to our understanding of historical ecological patterns. Well done Bibi and Cantalapiedra!