Anna K. Behrensmeyer, Smithsonian Institution; Kevin Hatala, Chatham University, and Purity Kiura, National Museums of Kenya

Human footprints stir the imagination. They invite you to follow, to guess what someone was doing and where they were going. Fossilized footprints preserved in rock do the same – they record instants in the lives of many different extinct organisms, back to the earliest creatures that walked on four feet, 380 million years ago.

Discoveries in eastern Africa of tracks made by hominins – our ancient relatives – are telling paleontologists like ourselves about the behavior of hominin species that walked on two feet and resembled us but were not yet human like we are today. Our new research focuses on footprints that amazingly record two different species of hominins walking along the same Kenyan lakeshore at the same time, roughly 1.5 million years ago.

Studying ancient tracks like these fills in exciting pieces of the human evolution story because they provide evidence for hominin behavior and locomotion that scientists cannot learn from fossilized bones.

Finding first fossilized footprints in Kenya

The first discovery of tracks of early hominins in Kenya’s Lake Turkana region happened by chance in 1978. A team led by one of us (Behrensmeyer) and paleoecologist Léo Laporte was exploring the geology and fossils of the rich paleontological record of East Turkana. We focused on documenting the animals and environments represented in one “time slice” of widespread sediments deposited about 1.5 million years ago.

We collected fossils from the surface and dug geological step trenches to document the sediment layers that preserved the fossils. The back wall of one of the trenches showed deep depressions in a layer of solidified mud that we thought might be hippo tracks. We were curious about what they looked like from the top down – what scientists call the “plan view” – so we decided to expose 1 square meter of the footprint surface next to the trench.

When I returned from more fossil bone surveys, Kimolo Mulwa, one of the expert Kenyan field assistants on the project, had carefully excavated the top of the mudstone layer and there was a broad smile on his face. He said, “Mutu!” – meaning “person” – and pointed to a shallow humanlike print in among the deep hippo tracks.

I could hardly believe it, but, yes, a humanlike footprint was clearly recognizable on the excavated surface. And there were more hominin tracks, coming our way out of the strata. It was awe-inspiring to realize we were connecting with a moment in the life of a hominin that walked here 1½ million years ago.

We excavated more of the surface and eventually found seven footprints in a line, showing that the hominin had walked eastward out of softer mud onto a harder, likely shallower surface. At one point the individual’s left foot had slipped into a deep hippo print and the hominin caught itself on its right foot to avoid falling – we could see this clearly along the trackway.

Even today on the shore of modern Lake Turkana, it’s easy to slip into hippo prints, especially if the water is a bit cloudy. We joked about being sorry our hominin track-maker didn’t fall on its hands, or face, so we could have a record of those parts, too.

Another set of tracks

Over four decades later, in 2021, paleontologist Louise Leakey and her Kenyan research team were excavating hominin fossils discovered in the same area when team member Richard Loki uncovered a portion of another hominin trackway. Leakey invited one of us (Hatala) and paleoanthropologist Neil Roach to excavate and study the new trackway, because of our experience working on other hominin footprint sites.

The team, including 10 expert Kenyan field researchers led by Cyprian Nyete, excavated the surface and documented the tracks with photogrammetry – a method for 3D imaging. This is the best way to collect track surfaces because the sediments are not hard enough – what geologists call lithified – to remove from the ground safely and take to a museum.

The newly discovered tracks were made approximately 1.5 million years ago. They occur at an earlier stratigraphic level than the ones we found in 1978 and are about a hundred thousand years older, based on dating of volcanic deposits in the East Turkana strata.

Who was passing through?

These footprints are especially exciting because careful anatomical and functional analysis of their shapes shows that two different kinds of hominins made tracks on the same lakeshore, within hours to a few days of each other, possibly even within minutes!

We know the footprints were made very close together in time because experiments on the modern shoreline of Lake Turkana show that a muddy surface suitable for preserving clear tracks doesn’t last long before being destroyed by waves or cracked by exposure to the Sun.

This is the first time ever that scientists have been able to say that Homo erectus and Paranthropus boisei – one our likely ancestor and the other a more distant relative – actually coexisted at the same time and place. Along with many different species of mammals, they were both members of the ancient community that inhabited the Turkana Basin.

Not only that, but with the new tracks as references, our analyses suggest that other previously described hominin tracks in the same region indicate that these two hominins coexisted in this area of the Turkana Basin for at least 200,000 years, repeatedly leaving their footprints in the shallow lake margin habitat.

Other animals left tracks there as well – giant storks, smaller birds such as pelicans, antelope and zebra, hippos and elephants – but hominin tracks are surprisingly common for a land-based species. What were they doing, returning again and again to this habitat, when other primates, such as baboons, apparently did not visit the lakeshore and leave tracks there?

These footprints provoke new thoughts and questions about our early relatives. Were they eating plants that grew on the lakeshore? Some paleontologists have proposed this possibility for the robust Paranthropus boisei because the chemistry of its teeth indicate a specific herbivorous diet of grasslike and reedlike plants. The same chemical tests on teeth of Homo erectus – the ancestral species to Homo sapiens – show a mixed diet that likely included animal protein as well as plants.

The lake margin habitat offered food in the form of reeds, freshwater bivalves, fish, birds and reptiles such as turtles and crocodiles, though it could have been dangerous for bipedal primates 4 or 5 feet (1.2 to 1.5 meters) tall. Even today, people living along the shore occasionally are attacked by crocodiles, and local hippos can be aggressive as well. So, whatever drew the hominins to the lakeshore must have been worth some risk.

For now it’s impossible to know exactly how the two species interacted. New clues about their behavior could be revealed with future excavations of more trackway surfaces. But it is fascinating to imagine these two hominin “cousins” being close neighbors for hundreds of thousands of years.

Ancient footprints you can visit

Earlier excavations of hominin trackways near a village called Ileret, 25 miles (40 km) to the north of our new site, are being developed as a museum through a project by the National Museums of Kenya. The public, the local Daasanach people, educational groups and tourists will be able to see a large number of 1.5-million-year-old hominin footprints on one excavated surface.

That layer preserves tracks of at least eight hominin individuals, and we now believe they represent members of both Homo erectus and Paranthropus boisei. Among these is a subset of individuals, all about the same adult size, who were moving in the same direction and appear to have been traveling as a group along the lake margin.

The museum built over the track site is designed to prevent erosion of the site and to protect it from seasonal rains. A community outreach and education center associated with the museum aims to engage local educational groups and young people in learning and teaching others about this exceptional record of human prehistory preserved in their backyard. The new site museum is scheduled to open in January 2025.

Anna K. Behrensmeyer, Senior Research Geologist and Curator of Vertebrate Paleontology, Smithsonian Institution; Kevin Hatala, Associate Professor of Biology, Chatham University, and Purity Kiura, Chief Research Scientist in Archaeology and Heritage, National Museums of Kenya

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Marie Ng, University of Washington

Nearly half of adolescents and three-quarters of adults in the U.S. were classified as being clinically overweight or obese in 2021. The rates have more than doubled compared with 1990.

Without urgent intervention, our study forecasts that more than 80% of adults and close to 60% of adolescents will be classified as overweight or obese by 2050. These are the key findings of our recent study, published in the journal The Lancet.

Synthesizing body mass index data from 132 unique sources in the U.S., including national and state-representative surveys, we examined the historical trend of obesity and the condition of being overweight from 1990 to 2021 and forecast estimates through 2050.

For people 18 and older, the condition health researchers refer to as “overweight” was defined as having a body mass index, or BMI, of 25 kilograms per square meter (kg/m²) to less than 30 kg/m² and obesity as a BMI of 30 kg/m² or higher. For those younger than 18, we based definitions on the International Obesity Task Force criteria.

This study was conducted by the Global Burden of Disease Study 2021 U.S. Obesity Forecasting Collaborator Group, which comprises over 300 experts and researchers specializing in obesity.

Why it matters

The U.S. already has one of the highest rates of obesity and people who are overweight globally. Our study estimated that in 2021, a total of 208 million people in the U.S. were medically classified as overweight or obese.

Obesity has slowed health improvements and life expectancy in the U.S. compared with other high-income nations. Previous research showed that obesity accounted for 335,000 deaths in 2021 alone and is one of the most dominant and fastest-growing risk factors for poor health and early death. Obesity increases the risk of diabetes, heart attack, stroke, cancer and mental health disorders.

The economic implications of obesity are also profound. A report by Republican members of the Joint Economic Committee of the U.S. Congress, published in 2024, predicted that obesity-related health care costs will rise to US$9.1 trillion over the next decade.

The rise in childhood and adolescent obesity is particularly concerning, with the rate of obesity more than doubling among adolescents ages 15 to 24 since 1990. Data from the National Health and Nutrition Examination Survey revealed that nearly 20% of children and adolescents in the U.S. ages 2 to 19 live with obesity.

By 2050, our forecast results suggest that 1 in 5 children and 1 in 3 adolescents will experience obesity. The increase in obesity among children and adolescents not only triggers the early onset of chronic diseases but also negatively affects mental health, social interactions and physical functioning.

What other research is being done

Our research highlighted substantial geographical disparities in overweight and obesity prevalence across states, with southern U.S. states observing some of the highest rates.

Other studies on obesity in the United States have also underscored significant socioeconomic, racial and ethnic disparities. Previous studies suggest that Black and Hispanic populations exhibit higher obesity rates compared with their white counterparts. These disparities are further exacerbated by systemic barriers, including discrimination, unequal access to education, health care and economic inequities.

Another active area of research involves identifying effective obesity interventions, including a recent study in Seattle demonstrating that taxation on sweetened beverages reduced average body mass index among children. Various community-based studies also investigated initiatives aimed at increasing access to physical activity and healthy foods, particularly in underserved areas.

Clinical research has been actively exploring new anti-obesity medications and continuously monitoring the effectiveness and safety of current medications.

Furthermore, there is a growing body of research examining technology-driven behavioral interventions, such as mobile health apps, to support weight management. However, whether many of these programs are scalable and sustainable is not yet clear. This gap hinders the broader adoption and adaptation of effective interventions, limiting their potential impact at the population level.

What’s next

Our study forecasts trends in overweight and obesity prevalence over the next three decades, from 2022 to 2050, assuming no action is taken.

With the advent of new-generation anti-obesity medications, obesity management could change substantially. However, the extent of this impact will depend on factors such as cost, accessibility, coverage, long-term efficacy and variability in individual responses. Future research will need to leverage the most up-to-date evidence.

The Research Brief is a short take on interesting academic work.

Marie Ng, Affiliate Associate Professor of Global Health, University of Washington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Liza M. Hinchey, Wayne State University

Political chasms, wars, oppression … it’s easy to feel hopeless and helpless watching these dark forces play out. Could any of us ever really make a meaningful difference in the face of so much devastation?

Given the scale of the world’s problems, it might feel like the small acts of human connection and solidarity that you do have control over are like putting Band-Aids on bullet wounds. It can feel naive to imagine that small acts could make any global difference.

As a psychologist, human connection researcher and audience member, I was inspired to hear musician Hozier offer a counterpoint at a performance this year. “The little acts of love and solidarity that we offer each other can have powerful impact … ” he told the crowd. “I believe the core of people on the whole is good – I genuinely do. I’ll die on that hill.”

I’m happy to report that the science agrees with him.

Research shows that individual acts of kindness and connection can have a real impact on global change when these acts are collective. This is true at multiple levels: between individuals, between people and institutions, and between cultures.

This relational micro-activism is a powerful force for change – and serves as an antidote to hopelessness because unlike global-scale issues, these small acts are within individuals’ control.

Abstract becomes real through relationships

Theoretically, the idea that small, interpersonal acts have large-scale impact is explained by what psychologists call cognitive dissonance: the discomfort you feel when your actions and beliefs don’t line up.

For example, imagine two people who like each other. One believes that fighting climate change is crucial, and the other believes that climate change is a political ruse. Cognitive dissonance occurs: They like each other, but they disagree. People crave cognitive balance, so the more these two like each other, the more motivated they will be to hear each other out.

According to this model, then, the more you strengthen your relationships through acts of connection, the more likely you’ll be to empathize with those other individual perspectives. When these efforts are collective, they can increase understanding, compassion and community in society at large. Issues like war and oppression can feel overwhelming and abstract, but the abstract becomes real when you connect to someone you care about.

So, does this theory hold up when it comes to real-world data?

Small acts of connection shift attitudes

Numerous studies support the power of individual acts of connection to drive larger-scale change.

For instance, researchers studying the political divide in the U.S. found that participants self-identifying as Democrats or Republicans “didn’t like” people in the other group largely due to negative assumptions about the other person’s morals. People also said they valued morals like fairness, respect, loyalty and a desire to prevent harm to others.

I’m intentionally leaving out which political group preferred which traits – they all sound like positive attributes, don’t they? Even though participants thought they didn’t like each other based on politics, they also all valued traits that benefit relationships.

One interpretation of these findings is that the more people demonstrate to each other, act by act, that they are loyal friends and community members who want to prevent harm to others, the more they might soften large-scale social and political disagreements.

Even more convincingly, another study found that Hungarian and Romanian students – people from ethnic groups with a history of social tensions – who said they had strong friendships with each other also reported improved attitudes toward the other group. Having a rocky friendship with someone from the other group actually damaged attitudes toward the other ethnic group as a whole. Again, nurturing the quality of relationships, even on an objectively small scale, had powerful implications for reducing large-scale tensions.

In another study, researchers examined prejudice toward what psychologists call an out-group: a group that you don’t belong to, whether based on ethnicity, political affiliation or just preference for dogs versus cats.

They asked participants to reflect on the positive qualities of someone they knew, or on their own positive characteristics. When participants wrote about the positive qualities of someone else, rather than themselves, they later reported lower levels of prejudice toward an out-group – even if the person they wrote about had no connection to that out-group. Here, moving toward appreciation of the other, rather than away from prejudice, was an effective way to transform preconceived beliefs.

So, small acts of connection can shift personal attitudes. But can they really affect societies?

From one-on-one to society-wide

Every human being is embedded in their own network with the people and world around them, what psychologists call their social ecology. Compassionate change at any level of someone’s social ecology – internally, interpersonally or structurally – can affect all the other levels, in a kind of positive feedback loop, or upward spiral.

For instance, both system-level anti-discrimination programming in schools and interpersonal support between students act reciprocally to shape school environments for students from historically marginalized groups. Again, individual acts play a key role in these positive domino effects.

Even as a human connection researcher, I’ve been surprised by how much I and others have progressed toward mutual understanding by simply caring about each other. But what are small acts of connection, after all, but acts of strengthening relationships, which strengthen communities, which influence societies?

In much of my clinical work, I use a model called social practice — or “intentional community-building” – as a form of therapy for people recovering from serious mental illnesses, like schizophrenia. And if intentional community-building can address some of the most debilitating states of the human psyche, I believe it follows that, writ large, it could help address the most debilitating states of human societies as well.

Simply put, science supports the idea that moving toward each other in small ways can be transformational. I’ll die on that hill too.

Liza M. Hinchey, Postdoctoral Research Fellow in Psychology, Wayne State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.