Infact
83 / 100
True

The text provides average penis sizes for gorillas, chimps, bonobos, and humans, and states that most primates have a penis bone and achieve erections through muscle contraction.

Infact verdict: True (83/100).

The claims regarding the average penis sizes of gorillas, chimps, bonobos, and humans are supported by reliable sources. The claim about most primates having a penis bone is also corroborated by multiple high-quality sources. However, the claim that primates achieve erections through muscle contraction is misleading, as it involves smooth muscle relaxation and arterial dilation rather than direct muscle contraction. Overall, the claims are mostly factual with some nuances in the biological mechanisms described.

August 11, 2026 Language: en 5 claims analyzed
How is this score determined? →

Individual claims

91
True Science
The average erect gorilla penis is 1.25 inches (3cm) long.
The claim is supported by multiple reliable sources, including The Guardian and IFLScience, which confirm the average size of an erect gorilla penis is about 1.25 inches (3 cm).
Fact Check Score None
Fact Check Weight 0
Web Consensus Score 90
Web Consensus Weight 40
Source Quality Score 85
Source Quality Weight 20
Llm Reasoning Score 80
Llm Reasoning Weight 40
Llm Reasoning Score Raw 80
Weighted Total 91
Evidence Summary 3 web sources confirm the claim.
91
True Science
The average chimp or bonobo penis is around 3.1 inches (8cm) long.
The claim is corroborated by reliable sources such as the Center for Academic Research and Training in Anthropogeny, which states that the average erect penis length for chimps and bonobos is around 8 cm (3.1 inches).
Fact Check Score None
Fact Check Weight 0
Web Consensus Score 90
Web Consensus Weight 40
Source Quality Score 85
Source Quality Weight 20
Llm Reasoning Score 80
Llm Reasoning Weight 40
Llm Reasoning Score Raw 80
Weighted Total 91
Evidence Summary 1 high-quality source confirms the claim.
91
True Science
The average human penis is around 5.1 inches (13cm) long.
The claim is supported by multiple sources, including PubMed, which states that the average erect penis length is around 13.12 cm (5.17 inches), aligning with the claim.
Fact Check Score None
Fact Check Weight 0
Web Consensus Score 90
Web Consensus Weight 40
Source Quality Score 85
Source Quality Weight 20
Llm Reasoning Score 80
Llm Reasoning Weight 40
Llm Reasoning Score Raw 80
Weighted Total 91
Evidence Summary 1 high-quality source confirms the claim.
94
True Science
Most primates, including chimpanzees, have a penis bone.
The claim is supported by multiple high-quality sources, including Wikipedia and The Guardian, which confirm that most primates, including chimpanzees, have a baculum (penis bone).
Fact Check Score None
Fact Check Weight 0
Web Consensus Score 95
Web Consensus Weight 40
Source Quality Score 90
Source Quality Weight 20
Llm Reasoning Score 85
Llm Reasoning Weight 40
Llm Reasoning Score Raw 85
Weighted Total 94
Evidence Summary 2 high-quality sources confirm the claim.
46
Mixed Science
Primates achieve erections through muscle contraction.
The claim is misleading. While muscle contraction plays a role, erections primarily involve smooth muscle relaxation and arterial dilation, as supported by sources like PMC and Springer.
Fact Check Score None
Fact Check Weight 0
Web Consensus Score 50
Web Consensus Weight 40
Source Quality Score 45
Source Quality Weight 20
Llm Reasoning Score 40
Llm Reasoning Weight 40
Llm Reasoning Score Raw 40
Weighted Total 46
Evidence Summary 2 medium-quality sources provide partial support.

Related fact-checks

Check any claim, instantly

Free AI-powered fact-checking — on every platform you already use.