11 Surprising Facts About Fungi Being Closer to Animals

By Trivia Daily, Staff Writer — Published November 8, 2026

Table of Contents

• Key Takeaways
• Why Fungi Closer Animals Matters for Science
• The Molecular Evidence That Changed Everything
• Frequently Asked Questions

When you think about mushrooms sprouting in your backyard or the yeast that makes bread rise, you probably don’t imagine them as distant relatives of your pet dog. Yet one of the most amazing discoveries in modern biology reveals that fungi closer animals than they are to plants. This surprising truth upended centuries of scientific classification and continues to fascinate researchers today. The evolutionary relationship between fungi and animals is written in their DNA, their cellular chemistry, and even the way they obtain energy from their environment.

For most of human history, fungi were lumped together with plants in scientific classification systems. They seemed plant-like enough, growing from the ground and staying in one place. But molecular biology has shown us a far more interesting story about these remarkable organisms.

Key Takeaways

• Fungi and animals share a more recent common ancestor than either does with plants, making them evolutionary cousins.
• Both fungi and animals store energy as glycogen, while plants use starch as their primary energy reserve.
• Fungal and animal cells lack chloroplasts and cannot produce their own food through photosynthesis.
• Chitin, the structural compound in fungal cell walls, is the same material found in insect exoskeletons and crustacean shells.
• Genetic analysis shows fungi and animals diverged from their common ancestor roughly one billion years ago.
• Both fungi and animals must consume organic matter for nutrition rather than synthesizing food from sunlight.

Why Fungi Closer Animals Matters for Science

The discovery that fungi share closer evolutionary ties to animals than to plants represents more than just a curiosity for trivia enthusiasts. This relationship has profound implications for medicine, agriculture, and our understanding of life’s diversity. When scientists develop antifungal medications, they face a unique challenge: because fungi and animals are so closely related at the cellular level, drugs that harm fungal cells often damage human cells too. This is why effective, safe antifungal treatments are much harder to develop than antibacterial drugs.

The fungal kingdom encompasses an estimated 2.2 to 3.8 million species, though only about 150,000 have been formally described. These organisms play crucial roles in ecosystems as decomposers, forming partnerships with plant roots, and even influencing animal behavior. Understanding their evolutionary position helps scientists explore these diverse functions and relationships.

The Molecular Evidence That Changed Everything

Before molecular biology techniques became available in the late 20th century, organisms were classified primarily by visible characteristics. Fungi looked enough like plants that the association seemed natural. Both appeared rooted in place, both had cell walls, and both reproduced through spores. The advent of DNA sequencing technology allowed researchers to compare genetic material directly, revealing relationships that physical appearance had hidden for centuries.

Ribosomal RNA analysis and other molecular techniques consistently showed that fungi branched off from the lineage leading to animals after both had already diverged from plants. The genetic similarities extend beyond simple ancestry markers. Fungi and animals share numerous genes involved in fundamental cellular processes that differ from plant versions of the same genes.

1. Fungi and Animals Store Energy the Same Way

Both fungi and animals use glycogen as their primary energy storage molecule. This complex carbohydrate serves as a readily accessible fuel reserve that cells can quickly break down when energy is needed. Plants, by contrast, store energy as starch, a chemically similar but structurally distinct polysaccharide. This shared biochemical strategy reflects the common ancestry of fungi and animals and represents a fundamental similarity in how these organisms manage their cellular energy economy.

2. Chitin Connects Mushrooms to Lobsters

The cell walls of fungi contain chitin, a tough, flexible polysaccharide that provides structural support. This exact same compound forms the exoskeletons of insects, spiders, and crustaceans like crabs and lobsters. No plants produce chitin naturally. This shared structural material is not coincidental but rather evidence of the evolutionary relationship between fungi and animals. The presence of chitin in both groups suggests their common ancestor also used this effective biological building material.

3. Neither Fungi Nor Animals Can Photosynthesize

Plants, algae, and certain bacteria can capture energy from sunlight and convert it into chemical energy through photosynthesis. Fungi and animals completely lack this ability. Both must obtain energy by consuming organic compounds produced by other organisms. Fungi secrete enzymes into their environment to break down organic matter externally, then absorb the resulting nutrients. Animals consume food and digest it internally. While the methods differ, the fundamental requirement to obtain pre-made organic molecules unites fungi and animals as heterotrophs, distinguishing them from autotrophic plants.

4. Genetic Analysis Places Fungi in the Opisthokonta Supergroup

Modern taxonomy groups fungi and animals together in a large classification called Opisthokonta. This supergroup is defined by organisms whose motile cells propel themselves with a single posterior flagellum. While most fungi don’t swim around as adults, certain primitive fungal groups and the reproductive cells of some species retain this characteristic swimming structure. Animals, particularly in their sperm cells, also display this trait. Plants and their close relatives belong to an entirely different supergroup, emphasizing the fundamental divide between these kingdoms of life.

5. Fungi and Animals Diverged About One Billion Years Ago

Molecular clock estimates, which use the rate of genetic mutations to calculate divergence times, suggest fungi and animals split from their common ancestor roughly one billion years ago. This ancient divergence occurred long before most of the familiar life forms we see today evolved. The common ancestor of fungi and animals was likely a single-celled organism living in ancient oceans. Over hundreds of millions of years, one lineage evolved into the diverse animal kingdom, while the other became the equally diverse fungal kingdom.

6. Both Lack Cell Wall Cellulose

Plant cell walls are primarily composed of cellulose, a structural polysaccharide that gives plants their rigidity. Animal cells lack cell walls entirely, while fungal cells have walls made of chitin and other compounds, but never cellulose. This absence of cellulose in both animals and fungi is another marker of their shared evolutionary history. The different structural strategies reflect each group’s lifestyle: animals developed mobility and flexible cell membranes, while fungi developed chitin-based walls suitable for their absorptive lifestyle.

7. Similar Cell Membrane Composition

The cell membranes of fungi and animals contain ergosterol and cholesterol respectively, which are structurally related sterols that help maintain membrane integrity and fluidity. Plants use entirely different compounds called phytosterols in their membranes. This biochemical similarity is why antifungal drugs often target ergosterol synthesis—the process is similar enough to animal sterol metabolism to be accessible to drug designers, but different enough to allow selective targeting. The challenge lies in the fine-tuning required to affect fungal cells without harming human ones.

8. Both Require Preformed Organic Nitrogen

Unlike many plants that can utilize simple inorganic nitrogen compounds from soil, both fungi and animals require more complex, organic nitrogen sources. They must break down proteins and other nitrogen-containing organic molecules to obtain this essential element. This shared nutritional requirement reflects similar metabolic pathways inherited from their common ancestor and represents another distinction from the plant kingdom’s more versatile nitrogen metabolism.

9. Fungi Have Genes for Collagen-Like Proteins

Researchers have discovered that some fungi possess genes encoding proteins structurally similar to collagen, the primary structural protein in animal connective tissue. While fungal versions serve different functions than animal collagen, the presence of related genes suggests these protein families existed in the common ancestor of fungi and animals. This genetic echo from the deep past provides molecular evidence for the relationship that DNA sequencing first revealed.

10. Shared Developmental Signaling Pathways

Certain cellular signaling pathways that control growth and development in animals also appear in fungi, though often adapted for different purposes. These shared molecular mechanisms, absent in plants, indicate that the toolkit for cellular communication and coordination was established before the fungal-animal split. The presence of similar signaling molecules and receptors in both groups demonstrates that evolution often modifies existing systems rather than inventing entirely new ones.

11. Both Produce Urea as a Metabolic Waste Product

Many fungi and animals produce urea as a nitrogen-containing waste product from protein metabolism. While the details vary—different species handle urea differently—the basic biochemical pathway that generates this compound is shared between the groups. Plants typically handle nitrogen waste through entirely different mechanisms. This shared metabolic waste product represents yet another biochemical similarity linking fungi to animals rather than plants.

Frequently Asked Questions

Are fungi more closely related to animals or plants?

Fungi are more closely related to animals than to plants. Molecular evidence shows fungi and animals share a more recent common ancestor, having diverged from each other roughly one billion years ago, long after both lineages had already separated from plants.

Why were fungi originally classified with plants?

Before DNA analysis became available, fungi were classified with plants because they appeared stationary, grew from substrates like soil, had cell walls, and reproduced via spores. These superficial similarities masked their true evolutionary relationships, which molecular biology later revealed.

What is the main difference between fungi and animals?

The main difference is how they obtain nutrients: fungi digest food externally by secreting enzymes into their environment and absorbing the breakdown products, while animals ingest food and digest it internally. Despite this difference, they share fundamental cellular and genetic similarities.

Do fungi and animals share any structural materials?

Yes, both fungi and animals use chitin as a structural material. Fungi incorporate chitin into their cell walls, while animals use it in structures like insect exoskeletons, crustacean shells, and even some internal structures. Plants do not produce chitin.

The next time you encounter a mushroom, consider that you’re looking at a distant cousin rather than a member of the plant kingdom. This fascinating relationship reminds us that life’s family tree holds surprises that challenge our everyday assumptions, and that the invisible world of molecules and genes often tells stories our eyes alone could never discover.