What Is the Closest Thing to a Human?

The question of “what is the closest thing to a human” invites exploration into our biological past and present. It prompts consideration of both living relatives and extinct species that once walked the Earth. Understanding these connections illuminates the intricate tapestry of evolution, revealing the shared heritage that binds us to other life forms and defines Homo sapiens.

Our Closest Living Biological Relatives

Among all living species, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) are considered our closest biological relatives. This close relationship is underscored by a remarkable genetic similarity; humans share approximately 98.8% of their DNA with them when comparing single nucleotide polymorphisms. This reflects a relatively recent shared ancestry.

Our lineage, along with that of chimpanzees and bonobos, diverged from a last common ancestor between 4.7 and 9.3 million years ago. Within the Pan genus, common chimpanzees and bonobos themselves separated more recently, approximately 1.7 to 2 million years ago. Some research indicates that bonobos might retain more anatomical features similar to this shared ancestor than common chimpanzees.

All great apes, including humans, chimpanzees, bonobos, gorillas, and orangutans, are classified under the family Hominidae. The particularly close kinship between humans, chimpanzees, and bonobos places them together in the tribe Hominini, highlighting their distinct evolutionary path within the primate order.

Shared Traits Beyond Genetics

Beyond the genetic blueprints, our closest living relatives exhibit a range of observable similarities in behavior, cognition, and physical attributes. These shared traits offer a glimpse into the foundational behaviors that predated the divergence of our species. For instance, chimpanzees in the wild are known to routinely use and even manufacture tools. They employ modified sticks to “fish” for termites, use stones to crack nuts, and fashion leaves into sponges for drinking water.

Complex communication is another parallel. While they do not possess vocal cords structured for human speech, chimpanzees and bonobos utilize a rich repertoire of gestures, facial expressions, and vocalizations. In controlled environments, individuals have demonstrated an ability to learn and use sign language or symbolic lexigrams to communicate complex thoughts and requests, showcasing underlying cognitive capacities for symbolic representation.

Evidence of problem-solving abilities and self-awareness is also present. Chimpanzees and bonobos can solve novel problems, adapt to changing environments, and exhibit self-recognition when presented with a mirror, a behavior once thought unique to humans. Their social structures are intricate, involving alliances, cooperation, and even instances of empathy and altruism. Physically, these apes share features like grasping hands, five fingers and toes, and the capacity for occasional bipedal locomotion, though they primarily move on all fours.

The Legacy of Extinct Human Species

While living great apes are our closest biological relatives, understanding “the closest thing to a human” also requires examining extinct relatives within the Homo genus. Neanderthals (Homo neanderthalensis) and Denisovans are particularly significant due to their close evolutionary relationship to modern humans. Neanderthals, for example, inhabited Eurasia for hundreds of thousands of years, demonstrating sophisticated behaviors previously attributed solely to Homo sapiens.

Neanderthals engaged in complex tool use, creating diverse stone tools for hunting and processing resources, a technology known as Mousterian. Evidence suggests they practiced symbolic thought, as indicated by findings of personal ornaments, burial practices, and potentially even cave art. Their ability to control fire and adapt to cold climates highlights their cognitive and adaptive prowess. Genetic studies have revealed interbreeding between Neanderthals and early Homo sapiens; non-African modern human populations carry a small percentage of Neanderthal DNA, typically between 1% and 4%.

Denisovans, known primarily from genetic evidence and limited fossil remains from Siberia, also interbred with modern humans, contributing to the genetic makeup of populations in Southeast Asia and Oceania. Other earlier hominin species, such as Homo erectus, represent important branches in our evolutionary tree, showcasing early migrations out of Africa and developing increasingly complex stone tool technologies, like the Acheulean handaxes. These extinct relatives underscore that humanity’s past was not a linear progression but a complex web of coexisting and interbreeding species.

Why Understanding Our Closest Relatives Matters

Investigating our closest relatives, both living and extinct, offers insights into human evolution and what defines our species. By studying chimpanzees and bonobos, we gain a clearer perspective on the shared behaviors and biological traits inherited from our common ancestor. This knowledge helps reconstruct the evolutionary steps that led to distinct human characteristics, such as advanced cognition, language, and complex culture. Observing their social structures and tool use provides a living laboratory for understanding the foundational elements upon which human societies developed.

The study of extinct human species, like Neanderthals and Denisovans, reveals a nuanced picture of human diversity and interconnectedness. Their genetic contributions to modern human populations demonstrate that our history involved interspecies encounters and shared survival strategies, challenging simplistic notions of human uniqueness. This historical context underscores that what makes us human is not a single, isolated trait but a combination of inherited capacities and unique adaptations.

This understanding carries implications for conservation efforts. Recognizing our close genetic and evolutionary ties to living great apes emphasizes their importance as parts of our shared biological heritage. Protecting these species and their habitats is a responsibility that stems from our interconnectedness. Exploring our closest relatives enriches our self-perception and appreciation for the intricate web of life.