Photo: iStock
Photo: iStock

How has the moon transformed our evolution?

Moon has remained important to the geology of the Earth and important to the evolution of life itself.

Chandrayan-3, India’s moon mission which was launched today, has set high hopes for India expecting its first moon soft landing. 

The small, silvery satellite of the Earth with an orbit if 384,400 kilometres, has a profound impact on lives on Earth. Though the Moon’s gravitational pull is weaker than Earth’s, it is responsible for Earth’s current length of the day, stable seasons and tides. It affects the everyday life of several species, including us. 

British historian Peter Frankopan, in his book The Earth Transformed, said, “The moon played a role not only in the transformation of the earth, but also in the development of life on this planet.” His book mentions how recent models suggest that big tidal ranges have been responsible for forcing bony fish into shallow pools on land, prompting the evolution of weight-bearing limbs and air-breathing organs.

The biggest impact that the moon has on life is through tides. The regular movement of water that exposes the land at the edge of the ocean and then covers it again just a few hours later could have encouraged life to adapt and move from the oceans to land. 

According to the Institute of Physics based in the United Kingdom, tides resulting from the gravitational force of the moon affect animal life in the intertidal zone, where the ocean meets the land between high and low tides. Weaker tides due to the absence of the moon would have narrowed down this zone, increasing the competition for survival among the species.

Billions of years ago, when the moon was closer to the Earth, extreme tides used to occur frequently because the Earth was spinning more rapidly. The tides eroded the coastal areas, adding minerals to the oceans which have been essential for life to evolve quickly.

Tides led by the moon also affect the reproductive cycles of marine life, where the laying and hatching of turtles’ eggs depend on the timings of tides. Often, their reproductive cycles coincide with different phases in the lunar cycle. Most other animal behaviours relating to the moon are because the tides change the coastal environment.

Lunar cycles affecting reproduction in animals

Frankopan, in his book, writes how ‘the reproductive cycles of many marine creatures are closely synchronised with lunar phases’, including migration and spawning in fish, crabs and triggering in plankton by the moon’s glow. It has also been noted that the timing and mating season of wildebeest in the Serengeti have been influenced by lunar phases.

‘The Moon has been up there as long as evolution has been taking place, and lunar rhythms are embedded in the life cycles of many organisms,’ told Tom White, senior curator of the Natural History Museum

Circalunar rhythms, which are tied to lunar cycles affect different types of organisms, according to White. He further explained how the Moon is essential to migration and navigation, particularly for birds. 

Frankopan also argued that lunar phases and moonlight are closely connected to the annual seasonal migrations of billions of species, especially birds.

The historian also linked lunar rhythms with human behaviour, activity and even fertility. The sleep cycles of the ‘pre-industrial communities’ were strongly influenced by lunar activity, he said. Frankopan also explained how long-term data from women’s menstrual cycles showed a correlation with lunar light and lunar gravity, with some scholars arguing that human reproductive behaviour was originally synchronous with the moon, but got modified recently by modern lifestyles.

Climate change and stabilsing seasons

The absence of moon would lead to extreme climate change. There would be huge differences between temperatures and daylight throughout the year, and ice ages would hit different parts of the world every few thousand years. Frankopan also stresses on this by writing how the moon’s gravitational pull helps transport heat away from the equator and towards the poles, fundamentally shaping earth’s climate.

Moon also stabilises the Earth's rotation on its axis by slowing Earth's rotation on its axis. In the absence of the moon, the poles would be burning hot and the equator freezing cold, seasons would be a thing of the past, and night and day would be equally long all year round.

Light of moon

Just like the planets, moon does not emit its own light but shines due to the reflection of the Sun’s light. Fluctuating light levels by the moon have a startling impact on life on earth. The ability to see and to be seen enhances in the moonlight. Studies have documented changes in the success rates of predators and foraging patterns of prey animals due to this added nighttime illumination.

Studies have shown that lions are less likely to hunt during the full moon and lion attacks on humans happen 10 days after the full moon. Many bats will be less active during the full moon.

The article also mentions how coral and certain species of crabs, worms and fish can sense the moonlight from particular phases of the Moon. They use this as a trigger to start species-wide reproduction. 

Nocturnal animals behave differently depending on where the moon is in the sky during its 29.5-day cycle. When the moon is full and bright, prey fish stay hidden in the reef, when they'd be most visible.

Tectonic plates, water distribution

Planetologists at the University of Münster (Germany) have shown, for the first time, that water came to Earth with the formation of the Moon some 4.4 billion years ago. 

The moon was formed when Earth was hit by a body called Theia. Researchers from Munster proved that Theia came from the outer solar system and delivered large quantities of water to Earth. 

According to the scientists, the collision that led to the formation of moon provided sufficient carbonaceous material to account for the entire amount of water on Earth.

The moon’s pull of gravity might have set our tectonic plates. It raises the level of the world’s oceans towards the equator. Without this gravity, the oceans would redistribute, raising levels at the poles. 

Down To Earth