Aging and longevity in the simplest animals and the quest for immortality

Area of Science:

• Evolutionary biology
• Gerontology
• Comparative anatomy

Background:

• Aging is a fundamental biological process.
• Understanding aging mechanisms in simple organisms offers insights into higher animals.
• Early life forms display varying degrees of longevity and potential immortality.

Purpose of the Study:

• To review longevity and potential immortality in early animal types.
• To contrast and compare these with humans and other higher animals.
• To explore the role of stem cells in longevity and regeneration.

Main Methods:

• Review of existing literature on aging and longevity in diverse animal groups.
• Comparative analysis of aging mechanisms across single-celled organisms, basal metazoans, and simple bilaterians.
• Discussion of evolutionary trade-offs between complexity and longevity.

Main Results:

• Single-celled organisms and basal metazoans (e.g., hydras, sponges) show remarkable longevity, sometimes immortality, linked to stem cells.
• Simple bilaterians, like flatworms, also possess high regenerative and rejuvenation capacities.
• Increased body complexity in higher animals is associated with reduced longevity and loss of immortality, likely due to tumor suppression mechanisms.

Conclusions:

• Pluripotent stem cells are key to longevity and regeneration in simple animals.
• Evolutionary trade-offs favored reduced longevity and immortality with increased complexity in higher animals.
• Understanding aging in simple organisms provides a foundation for studying aging in humans.