Do Humans Have a Fish Phase in the Womb?

Humans briefly have gill-like structures in the womb, offering fascinating clues to our evolutionary link to fish. This connection is visible not only in fossils but also within our own anatomy.

During early development in the womb, a human face forms from three main sections that rotate and merge together. This intricate process begins when the embryo is about the size of a grain of rice and continues until around 10 weeks. Uniquely, the top lip, jaw, and palate originate from gill-like tissues on the embryonic neck, reflecting our fishy ancestry. Though these tissues fuse seamlessly with no scars, the philtrum—the groove beneath the nose on the upper lip—remains as a subtle remnant of this fusion.

The timing of these tissue fusions is crucial. A delay of even an hour can cause cleft lips or palates, conditions affecting about one in 700 babies worldwide. The way the human embryo’s face forms mirrors a shared evolutionary pathway with many other vertebrates, highlighting our distant origins from fish.

Other anatomical features also reveal our aquatic heritage. For instance, shark gonads are located high in the chest, near the liver. Similarly, human gonads begin development high in the body but descend during growth. In women, they become the ovaries near the uterus, while in men, the testes travel a longer path down to the scrotum. This descent creates a natural weak spot in the abdominal wall, explaining why inguinal hernias—where gut tissue can protrude causing painful lumps—are far more common in men.

We Hiccup Because We Evolved From Fish

Solid evidence shows that humans did evolve from fish, but not from the modern types of fish we see today like cod or salmon. Our ancestors were a group of ancient lobe-finned fishes, called sarcopterygians, which lived about 375 to 425 million years ago.

Hiccups trace back to our fishy past. They result from spasms of the diaphragm muscle, controlled by nerves originally designed to regulate breathing through gills in fish. The nerve pathways in humans are more complex, increasing their susceptibility to spasms. The reflex that sustains hiccups comes from amphibian ancestors where it helped regulate air and water flow in the lungs and gills. While hiccups no longer offer any evolutionary advantage, they provide another fascinating connection to our aquatic origins.

In sum, features like the philtrum, the path of gonadal descent, and the mechanics of hiccups serve as anatomical evidence that humans evolved from fish, with remnants persisting through our development and physiology.

Creationist Rebuttal to the Claim of Human Embryonic Gills

Creationists argue that human embryos do not have gills as claimed by evolutionary biologists; rather, what are observed are pharyngeal pouches or clefts. These structures are not rudimentary gills but embryonic features that develop into parts of the ears, neck, and throat appropriate for humans and other terrestrial vertebrates. They emphasize that calling these “gill slits” reflects a biased interpretation aligned with Darwinian evolution rather than objective embryological facts.

According to creationist sources, these pharyngeal arches and clefts serve distinct developmental roles unrelated to respiration and bear no functional resemblance to fish gills. They view the notion that embryos “recapitulate” evolutionary history—that the embryo passes through a “fish stage”—as an outdated and widely discredited theory. Instead, they claim the embryo’s development follows a unique, purposeful, and fully functional path from conception to fetus, without stages representing evolutionary ancestors.

Scientific Refutation of the Creationist Rebuttal

Scientists acknowledge that the term “gill slits” is a simplification and that human embryos possess pharyngeal arches and pouches, not true gills. However, these structures are homologous to the gill slits seen in fish, meaning they share a common evolutionary origin even though they differentiate into different organs in mammals, birds, and reptiles.

Modern embryology explains that vertebrate embryos, including humans, develop similar patterns in their early stages due to shared ancestry. The pharyngeal arches are ancestral structures inherited from fish-like ancestors and have been adapted for various functions across species. This shared developmental framework is strong evidence for common descent.

Further, while the strict “recapitulation theory” (ontogeny recapitulates phylogeny) has been revised and nuanced, the broad concept that early embryonic stages reflect evolutionary relationships remains supported. Embryological similarities among vertebrates demonstrate evolutionary connections, confirmed by genetics and comparative anatomy.

For example:

All vertebrate embryos, including humans, fish, birds, and mammals, develop a notochord, a flexible rod-like structure that provides support during early development. This structure is a precursor to the vertebral column in vertebrates.
Vertebrate embryos exhibit pharyngeal arches or gill arches early in development. In fish, these develop into gills, but in humans and other mammals, they develop into structures of the face, ear, and neck such as the jawbone, Eustachian tubes, and tonsils.
Many vertebrate embryos share a tail structure at early stages which either becomes a tail in some species or partly regresses in humans, leaving the coccyx or tailbone.
Similarity in the three germ layers—ectoderm, mesoderm, and endoderm—that form all tissues and organs is conserved across vertebrates, reflecting a common developmental program.
The overall stages of development, from the formation of a blastula to gastrulation and organogenesis, follow a shared sequence across vertebrate species, although timing and specific structures vary.

These embryological parallels strongly support the evolutionary concept that vertebrates share a common ancestor, with genetic evidence providing the molecular basis for these developmental similarities. Modern science regards the presence of pharyngeal arches in human embryos as remnants of evolutionary history that have been co-opted into new functions, a common theme in evolutionary biology.