This year was another full of discoveries in human evolution that help us understand our origins and our closest evolutionary cousins, both living and extinct. With stories of our living ape relatives using medicine and information about the evolution of adolescence and emergence of genetic and neurological diversity, 2024 research delved into the human condition from a holistic perspective. New insights were made on early human relatives, including Neanderthals, Denisovans and their interactions with modern humans, as well as clues at interactions between hominins over one million years ago. New studies came from Indonesia, one of the most up and coming regions in human origins, and researchers reexamined hypotheses about one of our most popular fossil relatives, Homo naledi. Lastly, the world wished a happy 50th anniversary to the discovery of Lucy, one of the most famous fossil finds in the history of human evolution.

Our great ape cousins eat the same medicinal herbs we do

When you’re not feeling well, maybe you reach for some medicine or some comfort food that might even have medicinal properties (chicken soup, anyone?). Turns out our closest living evolutionary cousins, chimps, do this too. A study in June by Elodie Freymann and colleagues collected plant extracts from 13 species of trees and herbs in Uganda’s Budongo Central Forest Reserve that they observed chimpanzees eating but were not part of their normal diets to test them for anti-inflammatory and antibiotic properties. They found that 88 percent of the plant extracts inhibited bacterial growth, while 33 percent had anti-inflammatory properties. One of them is even used as a medicinal plant by East African communities to treat a variety of conditions today.

It’s not just chimps: A few months later in September, Leresche Even Doneilly Oyaba Yinda and colleagues reported their observation of wild western lowland gorillas in Gabon’s Moukalaba-Doudou National Park eating the same tree bark used by traditional healers with antibacterial abilities against drug-resistant E. coli. The gorillas also eat three other plants that are utilized in local medicine, although the antibacterial properties of the tree bark itself may explain why gorillas here can harbor E. coli bacteria without any symptoms. To round things out with our third great ape cousin, earlier this year in May, Isabelle Laumer and colleagues reported their observation of a wild male Sumatran orangutan applying sap from a climbing plant with known anti-inflammatory and pain-relieving properties commonly used in traditional medicine to his facial wound. Unlike the chimpanzees and gorillas passively consuming different medicinal plants, this is the first time any animal has been seen treating a wound directly with healing plants. The more we learn about our great ape cousins, the clearer it becomes that we aren’t that different after all.

Great apes also like to tease and joke around with each other

Two chimpanzees sit on a wooden platform; the chimp on the left is holding onto the shoulder and arm of the one on the right. Both look at each other, as if in mid-conversation.
In a study of great apes' playful antics, chimpanzees seemed to enjoy slapping adults, especially those that were dozing off. foshie via Flickr under CC BY 2.0 DEED

When our great ape cousins aren’t self-medicating, their lives are all work and no play—they spend all their time just finding food and mates, right? Well, a February study also by Isabelle Laumer and colleagues found that great apes like to tease, poke and pester each other too. While it may seem pretty lowbrow (even though apes have bigger brows than we do), this joking behavior requires an understanding of social norms and emotions that is cognitively complex. This understanding of emotions and social norms may have led to humor as we know it today. And if you’ve ever met a teenager, they sure like to tease each other more than just about any other age group. But did ancient people even go through a teenage stage? A September study by Mary Lewis and team investigated the bones of 13 European Upper Paleolithic adolescents aged between 10 and 20 years old. They found the first direct evidence that Ice Age teens went through puberty like teens do today, with signs of menstruation and voice changes. The ancient teens were generally healthy, and most entered puberty by the age of about 13, reaching full adulthood between 17 and 22 years old, suggesting that puberty in Ice Age teens began at a similar age to modern teens in wealthier societies today. This study is also the oldest application of a method called peptide analysis used for biological sex estimation.

There is evidence of genetic and neurological diversity in our hominin ancestors

Neanderthal skull
The cast of a Neanderthal skull on display at the Chemnitz State Museum of Archaeology in January 2023 Hendrik Schmidt / Picture Alliance via Getty Images

Oftentimes in human evolution, scientists only focus on the ‘typical’ or most common condition for individuals. Data on past genetic, neurological and physical diversity is usually more difficult to collect given the sparse nature of the fossil and archaeological record. However, this year multiple studies address the human condition from a more holistic perspective in both children and adults. A study published in June by Mercedes Conde-Valverde and team examined a Neanderthal temporal bone, the part of the skull that houses the middle and inner ear, from the site of Cova Negra in Spain. This bone comes from a Neanderthal child who exhibits multiple pathologies of the inner ear but still survived to at least the age of 6. The team examined six potential causes to account for the observed pathologies and concluded that Down Syndrome, caused by having three copies of the 21st chromosome, is the only option that accounts for all of them. This would make the fossil the first Neanderthal found with Down Syndrome, which also demonstrates Neanderthals caring for a child with a genetic and physical condition.

Speaking of Neanderthals, another trait in modern humans may be linked to their DNA in our own genomes: susceptibility to autism. A team led by Rini Pauly looked at probands (parts of our DNA that contribute to susceptibility to conditions) for autism and found that these parts of our genome tend to be enriched in Neanderthal-derived genetic data. These bits of Neanderthal DNA may have evolved in their population originally as a result of a genetic bottleneck in their population, predating any interbreeding with modern humans.

Lastly, another study this year examined the origins of ADHD, or Attention Deficit Hyperactive Disorder. The link between nomadic lifestyles and ADHD has been proposed before, but in February, a team led by David Barack applied that hypothesis to foraging. In an online foraging game, participants had to collect virtual berries and decide whether to continue depleting the resources or move to nearby patches. Participants then completed an industry standard ADHD screening test afterward. The team found that participants who met the threshold for ADHD not only moved on to nearby berry patches sooner than other participants, but they also got higher rewards from their virtual foraging overall. These findings suggest that ADHD traits may actually result in more optimal foraging, which could have conferred a survival advantage to our ancestors.

New ideas about how humans, Neanderthals and Denisovans lived continue to emerge

Bones embedded in dirt
Researchers discovered Thorin's fossilized remains in 2015 in a cave in southern France. Ludovic Slimak

This year has brought even more stories about our close relatives, the Neanderthals, including new updates on their interactions with our own species, Homo sapiens, and an update on our other evolutionary cousin, the Denisovans. First up, DNA analyses from a Neanderthal skeleton from Grotte Mandrin in France nicknamed “Thorin” revealed that this individual was part of a genetically isolated population and may have lived as recently as 42,000 years ago, overlapping with modern human presence on the European continent.

Published in September by Ludovic Slimak and colleagues, this research suggesting genetic isolation is surprising, indicating that this population of Neanderthals was not breeding with other known Neanderthal populations that would’ve been only a week or two away by foot. This makes us question our concept of Neanderthals as a monolithic, continuous population and suggests that they may not have been as cosmopolitan, interacting with each other regularly, as Homo sapiens did. Along similar lines, a series of papers published in January demonstrates that modern humans were occupying higher latitudes in the European continent earlier than previously thought. A study by Dorothea Mylopotamitaki and colleagues demonstrated that modern humans were present at the site of Ilsenhöhle in Ranis, Germany as early as 45,000 years ago. A companion paper by Sarah Pederzani and colleagues used stable isotope analyses of horse teeth at the same site to demonstrate that modern humans were in central Germany during one of the coldest phases of the last Ice Age, pointing towards our species’ ability to adapt to tough climates. Together, these studies present more of a patchwork or mosaic picture of modern human-Neanderthal occupation of the European continent lasting thousands of years.

Rather than looking at Neanderthal DNA in modern humans, a study from July by Liming Li and colleagues took the opposite approach and investigated modern human DNA in ancient Neanderthals. They discovered that a Neanderthal from Vindija, Croatia, had about 2.5 percent modern human DNA in its genome and another Neanderthal from the Altai mountains in Siberia had about 3.7 percent modern human DNA. Using these data, they also determined that there were two specific periods of gene flow from modern humans to Neanderthals, rather than this gene flow being consistent through time, and that the actual Neanderthal population sizes may have been about 20 percent lower than previous genetic-based estimates. Two pulses of genetic admixture indicate more than one migration event of modern humans out of Africa, and lower Neanderthal population sizes could indicate that their decreasing population was gradually being absorbed into our own, which might support one hypothesis of how Neanderthals ultimately went extinct.

We can’t forget the most mysterious member of our family tree, the Denisovans. Even though scientists know more about this species from genetic data than fossils, more physical specimens have slowly been popping up. Denisovan DNA is most prevalent in modern humans from eastern Asia through Indonesia and Oceania, and so far Denisovan fossils have been found from Siberia, Tibet, and Laos. At Baishiya Karst Cave in Tibet, a Denisovan mandible was published in 2019 dating to at least 160,000 years old. In July, Huan Xia and colleagues published another Denisovan fossil, a single rib, from this same site that dated to 48-32,000 years old. This extends the dates for Denisovan presence in the high-altitude Tibetan Plateau lasting over 100,000 years. Additionally, fossil animal remains from the same archaeological horizon had cut marks indicating processing for meat, marrow, hide and tools, shedding light on Denisovan behavior at the site.

Lastly, a study from October brings our three species together in the best way possible: through food. The AMY1 gene produces salivary amylase, an enzyme that helps us digest starches in food like grains and potatoes. Individuals exhibiting multiple copies of this gene have been linked to cultures that rely more heavily on starches for subsistence, like farmers, but the origins of this adaptation have been unclear. Feyza Yilmaz and colleagues found that the AMY1 gene multiple copy number adaptation actually emerged around 800,000 years ago, half a million years before Homo sapiens even existed. They found increased copy numbers of the AMY 1 gene in three Neanderthal genomes (2.6 to 5 copies) and one Denisovan genome (8 copies). These results suggest that the adaptation to multiple copies of the AMY1 gene evolved prior to our species’ divergence, and that starches may have been a staple food source well back into our lineage’s evolutionary history.

Footprints reveal ancient hominin interactions

Footprint imprint in sandy dirt
Researchers hypothesize that this footprint was made by a member of the hominin species Paranthropus boisei. Kevin Hatala / Chatham University

While stories about interactions between the more recent species of modern humans, Neanderthals and Denisovans aren’t unexpected these days, scientists are often only left to speculate about how earlier hominins may have interacted with each other. Without the ability to look at DNA for species over one million years old, the possibilities are limited. However, occasionally we get unusually lucky with preservation of other kinds of evidence. A study by Kevin Hatala and colleagues from November looks at fossilized footprints from East Turkana, Kenya dating to 1.4 to 1.6 million years old to determine who might have made the tracks. Analyzing the composition of the substrate the hominins walked on as well as the anatomy of the footprints themselves, the team found that one set of tracks from Koobi Fora in Kenya are very similar to modern human footprints.

Given the geological age and what early human fossils have already been found in this area, the team determined these tracks were most likely left by Homo erectus, the earliest hominin with a gait essentially the same as modern humans. Another set of tracks does not resemble modern human footprints but is still clearly left by a fully bipedal hominin. These tracks are most likely left by Paranthropus boisei, a member of a group of hominins not directly ancestral to our own species, but more like an evolutionary cousin. Even more exciting is that these tracks at Koobi Fora are only meters apart and were made by the two species within hours or days of each other, giving the strongest evidence to date that the two hominin cousins lived in the same area at the same time and likely interacted with each other.

Indonesia is a hotspot for human evolution

The next group of findings all highlight exciting discoveries in Indonesia, one of the current hotspots of new research in human evolution. The evolutionary history of the species Homo floresiensis, nicknamed “the hobbits” and only known from the island of Flores, Indonesia, remains a mystery. Is this species a shorter descendant of Asian populations of Homo erectus, known from the island of Java, Indonesia? Or did it evolve from an earlier and more ancestral hominin species, such as Homo habilis or Australopithecus afarensis? In August, Yousuke Kaifu and colleagues published the results of their search for fossils of “hobbit” ancestors at a site called Mata Menge on Flores, which confirmed their hypothesis that the early humans there were also small. Like, really small.

In 2013, they found a tiny limb bone fragment broken into several pieces in the 700,000-year-old layer at Mata Menge, which they thought was from a reptile until 2015 when Indra Sutisna, the curator of fossils at the Geology Museum in Bandung, Indonesia, recognized the bone as the shaft of a human upper arm bone. The team reported that this 700,000-year-old fossil from Mata Menge is the lower half of the upper arm bone of an adult ancient human. It came from an ancient human that stood only about 100 cm (just over three feet) tall, making this now the smallest upper arm bone known from the entire hominin fossil record. Given the early date of this bone, it seems that the first hominins on Flores were already small.

Elsewhere in Indonesia, in August Dylan Gaffney and colleagues published new evidence from Mololo Cave on Waigeo Island in the Raja Ampat archipelago of West Papua, that seafaring people traveled along a northern equatorial route through the humid tropics to reach islands off the coast of West Papua, Indonesia more than 50,000 years ago. This pushes back human occupation in the area by 10,000 years! The animal bones from Mololo Cave indicate that ancient people there hunted ground-dwelling birds, marsupials, and possibly megabats. To round out our Indonesia trifecta, in July, Adhi Agus Oktaviana and colleagues announced that they used a dating technique called laser-ablation U-series imaging to determine that a painting of a wild pig and three human-like figures in a limestone cave called Leang Karampuang in Sulawesi, Indonesia, which is dated to at least 51,200 years old, is now the world’s oldest figurative or representational cave art. This research suggests that visual storytelling including anthropomorphic figures and animals has a deeper origin in our species’ evolutionary history.

Did Homo naledi really bury their dead? Researchers examined the suggestion

Without a doubt, the Homo naledi fossil finds from Rising Star Cave in South Africa have been the talk of the town for the last several years as far as human evolution is concerned. A collection of small-brained, small-bodied, recently surviving (about 335,000 to 236,000 years old) hominins attributed to a new species found deep inside a complex cave system with nobody knowing how or why they got there? Of course that is going to draw attention. Many explanations have been offered to address this paleo mystery, including one hypothesis put forth last year by Lee Berger and colleagues that Homo naledi intentionally buried their dead in this cave system. However, this paper was a preprint, meaning that while it may have been peer-reviewed, the peer reviews were not incorporated into the final version of the papers before it was posted online. Therefore, this paper is technically “unpublished.” In two accompanying preprints, the same research team also suggested that Homo naledi used fire in the caves and produced rock art by etching the cave walls. This year, two different research teams conducted their own studies, examining whether the methodology was appropriate to address the intentional burial hypothesis and whether the evidence supported the intentional burial hypothesis like Berger and colleagues claimed.

The first of these papers from August by Kimberly Foecke and colleagues examined the methodology and evidence addressing the question of intentional burial. Foecke and team found issues with the overall theory, geochemical and sedimentological data, and data acquisition and quantification; they also highlighted mischaracterization and mis-quantification of statistical methods. This team demonstrated that despite all of that, even if the presented data is interpreted according to standards in the field, the hypothesis of intentional burial is not supported like the preprints claimed.

The second paper published in October by María Martinón-Torres and colleagues also examined the burial evidence claim. They found no anatomical articulation of skeletons, as would be expected in burials, no evidence for intentionally made burial pits, and bones from other individuals in the purported burials, concluding that there was no evidence for burial of Homo naledi remains. In the same paper, the team found no evidence for fire use, nor rock art or engravings. Both studies also expressed disappointment with Berger’s team for the lack of data, lack of methodological transparency, as well as poor hypothesis generation and testing. They suggest that in this instance, the preprint model, which is intended to facilitate open science, did not function as intended. To date, there have been no published peer-reviewed papers from Berger’s team regarding any of these claims.

We celebrated 50 years of Lucy

Lucy rendering
A sculptor's rendering of "Lucy," Australopithecus afarensis, at the Houston Museum of Natural Science on August 28, 2007, in Houston, Texas. Dave Einsel / Getty Images

We would be remiss if we didn’t end this year’s story with a shout-out to the 50th anniversary of the discovery of the most famous fossil in human evolution: AL 288-1, better known by her nickname, “Lucy.” Happy (Discovery) Birthday, Lucy! You may be 50, but you don’t look a day over 3.2 million.

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Ryan McRae

Dr. Ryan McRae is a paleoanthropologist studying the hominin fossil record on a macroscopic scale. He currently works for the National Museum of Natural History’s Human Origins Program as a contractor focusing on research, education, and outreach, and is an adjunct assistant professor of anatomy at the George Washington University School of Medicine and Health Sciences.

Briana Pobiner

Briana Pobiner is a paleoanthropologist with the National Museum of Natural History’s Human Origins Program. She lead's the program's education and outreach efforts.