What will to happen to the populations of light and dark moths on light trees?

Science requires that theories be tested to see if they are supported by evidence. During the 1950’s, Henry Bernard Davis Kettlewell ran a series of experiments and field studies to find out if natural selection had actually caused the rise of the dark peppered moth.

Dr. Kettlewell was an entomologist, a scientist who studies insects. In 1952, he was named a research fellow at Oxford, one of England’s premiere universities. He spent the rest of his life studying peppered moths and other moths known to turn dark through industrial melanism.

Scientists test theories by making predictions based on the theory. They then test the prediction to see if what they observe matches their expectations.

Hypothesis

Dr. Kettlewell thought that if natural selection caused the change in the moth population, the following must be true:

Heavily polluted forests will have mostly dark peppered moths. Clean forests will have mostly light peppered moths. Dark moths resting on light trees are more likely than light moths to be eaten by birds. The reverse should be true on dark trees. Dark moths in polluted forests would live longer than light moths, but dark moths in clean forests would die sooner.

Observation

Amateur entomologists across England helped Dr. Kettlewell map the population of light and dark peppered moths. Their work showed clearly that high populations of dark moths were found near the industrial cities producing pollution. In the countryside not darkened by factory soot, the dark moths were rare. Dr. Kettlewell compared this information with studies on the moth done in the past. It was clear that the dark moths were almost completely absent before the Industrial Revolution. Now they were found only where the forests were polluted.

Experiment

Light (top) and dark (bottom) peppered moth. Image by Jerzy Strzelecki via Wikimedia Commons.

To directly study bird predation on the moths, Dr. Kettlewell placed light and dark moths on the trunks of trees where he could observe them. He recorded the times a bird found the moth.

He found that on dark tree trunks, birds were twice as likely to eat a light moth as a dark moth. The same birds would find the dark moth twice as often if the bark on the tree was light. This supported the idea that dark moths had a survival advantage in a dark forest.

Dr. Kettlewell also tested the idea that dark moths live longer in dark forests. He collected groups of light and dark moths. All captured moths were marked so that they could be identified if recaptured. After marking them, both groups were released into the wild.

Two days later, moth traps were used to recapture the moths. In clean forests, twice as many light moths lived to be recaptured as the dark moths. Only half as many light moths were recaptured in polluted forests. He had experimentally shown that if the moth's color matched the environment, it had a better chance of survival.

Conclusions

In 1959, Dr. Kettlewell published an article in Scientific American summarizing his studies of the peppered moth. His years of work made an excellent case for natural selection. Every prediction he made had withstood the test.

In a dark forest, the dark peppered moths were shown to have a survival advantage over light moths. Birds were twice as likely to eat a light moth as a dark moth. Rare before factories were built in England, their increase in numbers was shown to be related to pollution. Natural selection was the best explanation for the change in the moth population over time.

Microsoft has responded to a list of concerns regarding its ongoing $68bn attempt to buy Activision Blizzard, as raised by the UK's Competition and Markets Authority (CMA), and come up with an interesting statistic.

In response to continued questions over whether Microsoft owning Call of Duty would unfairly hobble PlayStation, Microsoft claimed that every COD player on PlayStation could move over to Xbox, and Sony's playerbase would still remain "significantly larger" than its own.

Microsoft does not go into detail on its mental arithmetic here, but does note elswhere in its comments that PlayStation currently has a console install base of 150 million, compared to Xbox's install base of 63.7 million.

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That claim is part of a range of comments given to Eurogamer sister site GamesIndustry.biz in response to the CMA's latest report, which otherwise mostly repeats many of the same concerns raised by the UK regulator - and others around the world - already.

For those following the case, the CMA's latest intervention will not come as a surprise - it is the next step on the regulator's recent roadmap for how and when it will weigh in with its final ruling. This month, we were due the CMA's October "issues statement" - and it seems that this is the document to which Microsoft has now publicly responded.

The usual topics are covered - surrounding the potential for the deal to harm competitors should Microsoft gain too much of an advantage owning Activision Blizzard franchises (mainly, Call of Duty) and therefore being able to leverage their brand power to become a dominant market leader in the console market and cloud streaming.

Specifically, the CMA sees potential for the deal to harm Sony but also other streaming services such as Google (perhaps a moot point now), Amazon and Nvidia.

"Having full control over this powerful catalogue, especially in light of Microsoft's already strong position in gaming consoles, operating systems, and cloud infrastructure, could result in Microsoft harming consumers by impairing Sony's – Microsoft's closest gaming rival – ability to compete," the CMA wrote, "as well as that of other existing rivals and potential new entrants who could otherwise bring healthy competition through innovative multi-game subscriptions and cloud gaming services."

In response, Microsoft said such "unsupported theories of harm" were not enough to even warrant the CMA's current Phase 2 investigation - which was triggered on 1st September.

"The suggestion that the incumbent market leader, with clear and enduring market power, could be foreclosed by the third largest provider as a result of losing access to one title is not credible," Microsoft told GamesIndustry.biz.

"While Sony may not welcome increased competition, it has the ability to adapt and compete. Gamers will ultimately benefit from this increased competition and choice.

"Should any consumers decide to switch from a gaming platform that does not give them a choice as to how to pay for new games (PlayStation) to one that does (Xbox), then that is the sort of consumer switching behavior that the CMA should consider welfare enhancing and indeed encourage. It is not something that the CMA should be trying to prevent."

The CMA is due to notify Microsoft of its provisional findings in January 2023, at which point it can seek possible remedies to any sticking points raised. The regulator's final report - and overall ruling - will then be published no later than 1st March next year.

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