The history of bees on Earth stretches back far longer than the production of honey or the familiar buzz of a backyard hive. The lineage of the bee is one of immense geological antiquity, preceding the appearance of many well-known groups of mammals and birds. Their existence spans a period that witnessed dramatic shifts in global flora, originating during the age of the dinosaurs. The story of their time on the planet is marked by a fundamental dietary shift that permanently altered the course of life on land.
The Evolutionary Jump: From Wasp to Pollinator
The first insects recognizable as bees evolved from a predatory ancestor: carnivorous hunting wasps within the superfamily Apoidea. This foundational change was a transition from provisioning their young with paralyzed insects to feeding them entirely on flower pollen. This crucial dietary switch, known as pollinivory, marks the origin of the entire bee clade, Anthophila.
The fossil record links this evolutionary moment to the mid-Cretaceous period, approximately 100 million years ago. The earliest definitive fossil evidence comes from a specimen trapped in Burmese amber, named Melittosphex burmensis. This ancient insect is a transitional form, displaying features of both its wasp ancestors and modern bees. It possessed slender wasp-like hind legs, yet it also exhibited branched hairs on its body, a specialized adaptation for collecting pollen.
The discovery of Melittosphex suggests that the key innovation for the bee lineage was the development of these specialized, branched hairs, known as scopae, which efficiently capture and carry the fine powder. Phylogenetic analysis suggests the bee lineage itself may have originated slightly earlier, around 123 million years ago, in the Early Cretaceous. Regardless of the exact date, this evolutionary jump established the new insect group, which quickly expanded its role as a collector of floral resources.
The Critical Relationship with Flowering Plants
The success of the newly evolved bee lineage was intimately tied to the simultaneous rise of flowering plants, or Angiosperms. This pairing is a classic example of co-evolution, where two groups influenced each other’s diversification and success. By the Middle to Late Cretaceous period, Angiosperms were undergoing an ecological explosion, becoming the dominant form of plant life. This rapid spread provided the early bees with a stable and abundant food source.
The morphological features of these early flowers influenced the development of different bee body types. As flowers evolved various shapes, colors, and nectar depths, bees specialized to access these resources, leading to adaptations in tongue length and body size. The diversification of the major bee clades, including all seven extant families, is estimated to have occurred during this same period, driven by the expanding floral diversity. This ecological partnership meant that as Angiosperms became more species-rich, the bees that pollinated them also diversified rapidly to fill the new ecological niches offered by floral morphology.
The Great Diversification: Solitary and Social Life
Following the co-evolutionary push with flowering plants, the bee lineage continued to diversify, resulting in the vast spectrum of species observed today. The earliest bees were solitary, with each female constructing and provisioning her own nest. Over 90% of the approximately 20,000 known bee species are solitary, including the ground-nesting Andrenidae and the cavity-nesting Megachilidae.
The evolution of complex social behavior, known as eusociality, is a more recent development in bee history, occurring independently in several lineages. The earliest evidence for eusociality is estimated to have appeared in corbiculate bees, which include honey bees and bumble bees, at least 87 million years ago. This transition involved the development of overlapping generations, cooperative brood care, and a reproductive division of labor.
The most advanced forms of eusociality, seen in honey bees and stingless bees (both within the family Apidae), evolved independently from a primitively eusocial ancestor. This represents the final stage of their evolutionary journey, where the initial solitary insect gave rise to highly organized colonies that function as a single unit.