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why humans (and mammals in general) don’t poop and pee out of one hole like birds and lizards.

Dr. Aris Thorne
Dr. Aris Thorne
Senior Science Editor · Mar 21, 2026 · Updated Apr 13, 2026

TL:DR – It's literally just the way our tracts work. Birds and lizards have completely different systems than humans. When you drink something or eat food with fluids, it gets absorbed into your body to get the nutrients and is flushed through the kidneys into the bladder.

99
Words

1 min
Read Time

#104
of 500 in Animals

+46%
vs Category Avg

The Short Answer

TL:DR – It's literally just the way our tracts work. Birds and lizards have completely different systems than humans. When you drink something or eat food with fluids, it gets absorbed into your body to get the nutrients and is flushed through the kidneys into the bladder. The solid mass of food you eat that isn't absorbed due to lack of nutrients are passed on as poop. One goes through your gastrointestinal tract while the other goes through your kidneys. Simple as that. There are also mammals that poop and pee out of the same hole, called Monotremes.

Analysis

Key Concepts: Food, absorbed, nutrients

This explanation focuses on food, absorbed, nutrients and spans 99 words across 7 sentences. At 46% above the average Animals explanation (68 words), this is one of the more thorough answers in this category, reflecting the complexity of the underlying question.

What This Answer Covers

The explanation opens with: “TL:DR – It's literally just the way our tracts work.” It then elaboratesultimately building toward a complete picture across 7 connected points.

How This Compares in Animals

Ranked #104 of 500 Animals questions by answer depth (top 22%). This places it in the comprehensive tier — the top quarter of most thoroughly answered questions. Questions at this depth typically involve multi-faceted topics requiring nuanced explanation.

Frequently Asked Questions

Is there a simple explanation for why why humans (and mammals in general) don't poop and pee out of one hole like birds and lizards.?

TL:DR – It's literally just the way our tracts work. Birds and lizards have completely different systems than humans. When you drink something or eat food with fluids, it gets absorbed into your body to get the nutrients and is flushed through the…

How detailed is this explanation compared to similar Animals questions?

This is one of the most thorough answer at 99 words, ranked #104 of 500 Animals questions by depth. The key concepts covered are food, absorbed, nutrients.

What approach does this answer take to explain why humans (and mammals in general) don't poop and pee out o?

The explanation uses direct explanation across 99 words. It is categorized under Animals and addresses the question through 1 analytical lens.