Nocturnal bottleneck

The nocturnal bottleneck hypothesis is a hypothesis to explain several mammalian traits. In 1942,

Mammals evolved from

Numerous features of mammalian physiology, especially features relating to the sensory organs, appear to be adaptations to a nocturnal lifestyle. These include:

Senses

• An acute sense of hearing, with coiling
  pinnae and auditory ossicles
  in the ear.
• Very good sense of smell, well developed
  nasal turbinates. Most mammals have a large olfactory bulb
  .
• Well-developed sense of touch, particularly the whiskers.^[7]
• With the exception of
  higher primates, very large cornea, giving a less acute visual image compared to birds and reptiles.^[8]
• Limited
  colour vision.^[9]

• Endothermia that enabled early mammals to become independent of solar radiation and environmental factors.^[1]
• Unique type of brown adipose tissue, allowing mammals to generate heat quickly.^[10]
• Mitochondria with respiration rates five to seven times higher than those of reptiles of similar size.^[11]
• Fur to assist in thermo-regulation in a cold (night) environment.
• Lack of an ocular shielding mechanism against (diurnal) ultraviolet light.^[12]
• Loss of the ability to produce gadusol, a chemical which protects against the sun.^[13][14]
• The photolyase DNA repair mechanism, which relies on visible light, does not work in the placental mammals, despite being present and functional in bacteria, fungi, and most other animals.^[15][16]

Behaviour

• placentals.^[17][18]
• Burrowing lifestyle allowing sheltering from climate and diurnal predators appears to be a basal mammalian trait.^[19]