That makes sense. I expect mammals are more complex than worms.
Far more.
Note that “worms” like earthworms or maggots are utterly different from flatworms.
Flatworms are acoelomate (lacking a body cavity) and triploblastic (three germ layers: ectoderm, mesoderm, endoderm), but their body plan is rudimentary. They have a gastrovascular cavity for digestion (no true anus), protonephridia for excretion/osmoregulation, and lack dedicated circulatory or respiratory systems—relying on diffusion for gas exchange and nutrient transport.
Insects, in contrast, are coelomate arthropods with a segmented body, exoskeleton (chitin-based), jointed appendages, and tagmatization (head, thorax, abdomen). They possess an open circulatory system (hemolymph), tracheal tubes for respiration.
Flatworms have a basic centralized nervous system (CNS) with a bilobed “brain” (cephalic ganglion) containing several thousand neurons, two ventral nerve cords, and peripheral nerves for sensory input (e.g., touch, chemoreception via eyespots.
Neuron counts in insects range from ~100,000–200,000 in fruit flies to ~1 million in cockroaches or bees, enabling complex behaviors such as social coordination, navigation, and associative learning. Quantitatively, insects have 50–200 times more neurons than flatworms (which have ~5,000–20,000 neurons total)
Mammals are coelomate, triploblastic vertebrates with a vertebral column, endoskeleton, and highly differentiated organ systems.
Neuron counts are vast: mice have ~70 million, humans ~86 billion. This enables abstract thinking, social behavior, and tool use. Flatworms’ simple CNS pales in comparison, with mammals having 10,000–10,000,000 times more neurons (~5,000–20,000 in flatworms).
The comparison between a flwtworm, insct and human is like a stone carved wheel compared to a bicycle to a F1 race car