Rosa Rubicondior: Unintelligent Design - The Prolific Waste of Spawning Coral

Tuesday, 13 October 2026

Unintelligent Design - The Prolific Waste of Spawning Coral

Spawning coral release quintillions of eggs each year: new research

spawning coral on the Great Barrier Reef, Australia

One of the most conspicuous features of the living world is its reproductive extravagance. Organisms manufacture enormous quantities of eggs, sperm, seeds and spores, only for the overwhelming majority to leave no descendants. Coral spawning provides a spectacular example: an underwater blizzard of reproductive material, produced at considerable biological expense, from which only a tiny fraction will ultimately contribute to the next generation of breeding corals. If this is intelligent design, its designer appears remarkably comfortable with failure on an industrial scale.

New research by M. M. Bilodeau and K. M. Quigley, published in Ecology and Evolution puts a staggering figure on this reproductive output. The researchers estimate that Indo-Pacific corals could produce approximately 3.46 quintillion eggs — 3.46 × 10¹⁸ — during a single hypothetical spawning period. This is a first approximation based on reproductive traits and coral cover, with missing measurements estimated from other traits. It is neither a direct count nor a precise total for all coral reproduction worldwide each year.

Each egg and sperm normally carries one set of chromosomes: half the usual chromosome complement of the parent’s body cells, including a reshuffled selection of its inherited genetic variants. Producing these cells requires resources, and eggs also contain provisions for early development. Yet many gametes never achieve fertilisation, while many resulting larvae fail to establish themselves and survive to reproductive maturity. The study estimates the scale of egg production, not the precise proportion lost, but the distinction between producing eggs and producing successful descendants is fundamental.

This is the sort of extravagance I discuss in my book, The Unintelligent Designer: Refuting The Intelligent Design Hoax. The waste here is reproductive: material that fails to transmit the parent’s genes to another breeding generation. Some of it feeds other organisms or returns nutrients to the ecosystem, but that does not turn an unsuccessful reproductive investment into a successful one for the coral that made it.

Evolution readily explains how such a system can arise. Natural selection can favour producing vast numbers of relatively inexpensive reproductive cells when that strategy yields more surviving offspring than available alternatives. Synchronised spawning improves the prospects of fertilisation, while sheer numbers help compensate for losses. Resource costs still matter, but selection favours reproductive success within existing constraints; it does not require every gamete to succeed. There is no foresight, no concern for the fate of each individual egg, and no requirement for an economical system by human engineering standards.

For advocates of a perfect, all-knowing designer, the question is rather more awkward. Why would a being supposedly responsible for both the organisms and their environment arrange reproduction around such enormous losses? Calling this a clever way of overcoming the hazards of ocean life merely leaves unanswered why the same designer imposed those hazards in the first place. Coral spawning makes sense as an evolved compromise. Its spectacular abundance provides little reason to mistake that compromise for evidence of perfect planning.

One of the authors of the paper in Ecology and Evolution, Kate Marie Quigley of James Cook University, has also written about these findings in an article in The Conversation. Her article is reprinted here under a Creative Commons license, reformatted for stylistic consistency.

Published: October 13, 2026 7.54pm BST

Spawning coral release quintillions of eggs each year: new research

Auscape / Getty Images

Kate Marie Quigley, James Cook University

Most kinds of coral spawn once a year. In an enormous multi-day event synchronised to specific phases of the moon, they release vast slicks of eggs and sperm into the ocean to be mixed together by the drifting currents.

Imagine hundreds of thousands of Olympic swimming pools filled with tiny pinkish spheres, all dumped into the sea at once.

In new research published in Ecology and Evolution, my colleague and I have for the first time estimated just how many eggs are involved in one of these spawnings, and it’s a mind-boggling number.

According to our calculations, in a single spawning event, corals across the Indo-Pacific region release around 3.5 quintillion eggs (that’s 3,500,000,000,000,000,000 if you write out all the zeroes).

This isn’t a just a curious piece of trivia, either: it’s basic information we need to help preserve Earth’s coral species for the future.

Coral spawn form large pinkish slicks in the ocean.

Credit: Philippe Max Rouja.

Why count coral eggs?

Counting Earth’s ecological assets reveals how our planet functions. Knowing the total number of ants living in the ground (around 20 quadrillion) allows scientists to estimate how much carbon they can remove, for example.

Scientists have mapped half a trillion adult coral colonies, as well as tracking global fish egg production. These numbers tell us about the function and health of ecosystems.

Counting nature also tells us about its power to regenerate. Ocean life, and coral reefs in particular, are bearing the brunt of global warming. Since 1950, roughly 50% of global coral reef cover has disappeared.

This is why we want to know about coral’s capacity to reproduce and regenerate.

A baseline for coral reproduction

Our new study provides the first estimate of coral reproductive potential across the Indo-Pacific region, which is a hotspot for marine biodiversity.

Our estimate of 3.5 quintillion eggs released in a spawning establishes an essential baseline of what these reefs produce at peak capacity.

Measuring across hundreds of coral species, we found most eggs came from a few key groups. Branching Acropora, Porites (bommies or massive boulder corals), and Montipora accounted for around half the total egg supply.

How to count a quintillion eggs

How did we figure this out? We were looking at almost 190,000 square kilometres of tropical reef, so we couldn’t just swim out with a clipboard and start counting eggs.

Instead, we looked at what we knew about coral and eggs at the small, medium and large scales.

First we examined coral polyps. A single coral is a colony of many, many individual polyps. We calculated how many eggs fit inside the average polyp.

Next we estimated how many polyps are in each whole coral. This let us work out how many eggs an average-sized colony of each coral species produces.

Finally, we combined these figures with real-world data about coral cover and geographic distribution for hundreds of species.

This might seem like a straightforward process, but direct counts of eggs only exist for a handful of coral species. It’s a tricky task, and for many species we still don’t even know exactly when they spawn.

To fill in the gaps in the data, we made estimates based on patterns in data from related species.

Not all coral species are equal

We discovered many interesting things about coral egg production. Massive boulder corals produced the most eggs per square centimetre of living tissue, for example, while branching corals dominated overall egg production across the region.

So, our research uncovered an important scale mismatch. This means that polyp or colony-level output does not necessarily translate to high regional egg output.

We also found that while some groups of species produced fewer eggs on average, there were individual species within those groups that were highly productive egg factories.

Even within the group of branching Acropora species, one species produced ten times more eggs per square centimetre than the others.

This kind of species-level information tells us about what might be the true workhorses of reef repair. We need more of it – and that means genuine species-level measurements.

What now?

Why is this so critical for reef conservation? Reproduction is the fundamental bridge to recovery after severe marine heatwaves. Damaged reefs cannot recover without a supply of fresh coral babies onto the reef.

Our study provides a practical, data-driven blueprint for coral protection and rehabilitation. Knowing that a handful of coral groups carry most of the potential for repair, managers and conservationists can deliver their attention to these heavyweights.

Our work is what is called a “first-order” estimate: a rough draft with a large (but quantifiable) amount of uncertainty. It’s a good start, as it allows us to get an idea of the scale of coral reproduction and the differences between coral groups.

We now need to refine our estimates by going out and directly measuring egg release across new and diverse coral species. It’s an exciting but also daunting prospect – 190,000 square kilometres is a lot of area to cover with a clipboard.
Kate Marie Quigley, DECRA Research Fellow in molecular ecology, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Published by The Conversation.
Open access. (CC BY 4.0)

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ABSTRACT
Coral reproductive potential is a fundamental component of reef resistance and recovery, yet large-scale estimates of reproductive potential remain limited. This study generated the first large-scale approximation of coral reproductive potential across the Indo-Pacific by integrating coral fecundity, trait-based imputation, and coral cover data. Reproductive potential was estimated for 277 coral species from 55 genera, including key genera such as Acropora, Isopora, Montipora, and Porites, for a single, hypothetical spawning period. We combined empirical coral fecundity datasets with trait-based imputation approaches to estimate reproductive potential at three levels: fecundity per cm², colony fecundity, and total fecundity across the Indo-Pacific. These fecundity estimates were then integrated with regional coral cover to derive a first-order approximation of reproductive potential. The estimated total reproductive potential of Indo-Pacific corals was approximately three quintillion eggs (3.46 × 10¹⁸) for one hypothetical spawning period. Fecundity varied significantly across genera and growth forms, with Isopora, Acropora, and Montipora contributing disproportionately to total egg production (mean totals of 3.9 × 10¹⁶, 4.2 × 10¹⁵, and 3.49 × 10¹⁵ eggs, respectively). Branching and massive growth forms collectively accounted for roughly 50% of total fecundity across all levels. Species-level fecundity was not consistently aligned with genus-level trends, with some species exhibiting exceptionally high fecundity at the species level despite relatively low average fecundity at the level of genus. Concordance across the three fecundity levels was low, highlighting substantial variation within genera and potential gaps in our current understanding of coral reproductive potential, likely both. This study provides the first quantitative approximation of Indo-Pacific coral reproductive potential, demonstrating high variation across species, genera, and growth forms. These findings underscore the importance of multi-scale reproductive assessments and offer a data-driven foundation for identifying key taxa for conservation or restoration efforts based on their disproportionately high contribution to reef recovery.

Bilodeau, M. M., and K. M. Quigley. 2026.
Patterns in Coral Fecundity Across the Indo-Pacific.
Ecology and Evolution 16(10): e74441. https://doi.org/10.1002/ece3.74441.

Copyright: © 2026 The authors.
Published by John Wiley & Sons, Inc. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The remarkable feature of coral spawning is therefore not simply the number of eggs produced, but the gulf between reproductive output and reproductive success. Each gamete represents an investment of resources and carries genetic material that could contribute to another generation. Almost all will fail to do so, either because fertilisation never occurs or because the resulting offspring do not survive to reproduce. The spectacle is impressive, but abundance should not be confused with efficiency.

There is no difficulty explaining this in evolutionary terms. Natural selection favours heritable characteristics that improve reproductive success under prevailing conditions, even when the successful strategy involves enormous losses. Producing many small reproductive units can yield a better return than producing fewer, more expensive ones. Such a strategy requires neither foresight nor a plan: it persists because, within the constraints of coral biology and the marine environment, it has enabled successive generations to leave descendants. Its apparent wastefulness is entirely compatible with its evolutionary effectiveness.

The difficulty arises when this evolved compromise is presented as the work of a supreme intelligence. An engineer obliged to work within an existing hazardous environment might reasonably adopt such a strategy; an omnipotent designer supposedly responsible for the environment itself has no such excuse. Invoking the needs of predators or the recycling of nutrients merely shifts the question to why the entire system was arranged around reproductive failure. As I argue in The Unintelligent Designer: Refuting The Intelligent Design Hoax, nature’s extravagance is readily understood as the outcome of evolution without foresight. Calling it perfect design adds an assertion, but no explanatory value and simply invites criticism of the putative designer as grossly incompetent.

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