QI British TV Programme - Raspberry Bush

I just watched an episode of QI (for American friends it used to be hosted by Stephen Fry, now Sandi Toksvig, and is about general ignorance) and one item featured a raspberry bush. I really dislike when people who believe evolution anthropomorphise non-human things by way of explanation. In this item the question was asked - if a raspberry bush needs to disperse its seeds by encouraging animals to eat them, why does it have prickles?

Answer - it wants a particular sort of animal that isnt put off by a prickle. Birds and small rodents arent bothered by the prickles or thorns, they can dodge round them, and they are the ones that will take the seeds long distances, and that is ‘what the bush wants’. But a bear or other large mammal in contrast will digest the seeds and what’s left will be dumped in a single pile of manure, and so dont disperse the seeds. Or as one comedian said, they make them into jam and sell them…

Firstly I hated when she said ‘it’s what the bush wants’ as if the bush has a brain and thinks. Ive heard similar language from professional evolutionists so I suppose it’s not surprising tv hosts use it too. But I assume all would agree it’s nonsense language?

But secondly, could someone well grounded in evolution please explain the mechanisms that are behind prickles being present in for example raspberry bushes, which do seem to put off certain animals from eating them, whilst encouraging others to eat them, for example birds, if indeed that is the case.

When I hear such explanations, it is hard not to think of ‘design’ though of course such tv hosts are oblivious to that as theyre atheists. Is the spreading of their seed over longer distances on purpose, or just a coincidence, given a fruit plant does not ‘think’ and isnt aware of where its seeds end up.

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Having tried to raise thornless blackberries outside of a fenced area, I can testify that deer will strip them bare of leaves overnight, and there will be no blackberries for anybody. The thorns have little to do with who eats the fruit, but a lot to do with making fruit.
From a theistic standpoint they are a good adaptation for blackberries, and only becomes a negative for people when they are harvesting them.


So a raspberry bush has no needs?

You remind me of when people pushed some nonsense about animals and infants feel no pain. People believed whatever was convenient for them in regards to those who could not defend themselves verbally.

Doing things for their own reasons is the very essence of what life means. And this is just as true of the raspberry bush as it is with human being. What they do is intentional even if they cannot defend themselves against BS to the contrary in a court of law – even if they don’t have a nervous system to send pain messages.

So yes I am saying all living things are conscious – not to the same degree of course. But all of them are collecting information about themselves and their environment in order to respond to things which are contrary to their needs. It is a big difference to be sure and the consciousness of a raspberry bush is nearly insignificant in comparison to that of a human being. But it is not zero and yes the raspberry bush does have its own needs even if it doesn’t have the concept of a need or the ability to communicate their needs to us.

I would not say nonsense, as it is (conjectured) to achieve some desirable end for the plant. We as humans want desirable ends, so it constitutes a reasonable anthropomorphism. Most people are are not going to be mislead into thinking plants have brains, so it is more casual than nonsense. In contrast to edutainment, journal papers are comparatively free of anthropomorphic language.

But I hasten to agree that variation, selection, and drift have no distant objective. The narration of life finding a way, some brilliant solution to a problem, popularized narrative is often way overdone, and can be misleading in the same way creationists often indulge in the Texas Sharpshooter Fallacy.

As for the push - pull of thorns and fruit, I can only offer unqualified opinion worth what I am charging, but my first thought would be to note that while there may be an advantage to the plant to have its fruit eaten, there is only disadvantage to the rest of the plant being eaten by anything; so plants have developed a number of traits, including thorns, in defense.

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Small rodents do not take the seeds long distances. Large mammals can do that and give a proper nutrient boost to those seeds that germinate in the scats or dung. Larger carnivores or omnivores are interested of sweet (ripe) berries so they pick the berries at the correct moment, not before the seeds are ready. The good side of large mammals (other than ruminants) is also that they do not break the seeds, they swallow the berries only partly crushed. If the seeds are not crushed, a large part remain viable after they have passed through the animal.

Birds are also good candidates for long distance dispersal, although the stones in the crop of a bird will crush many seeds. Birds select berries based on color, so they are also eaters that pick the berries at the correct time.

If there are browsers around, bushes that have defence mechanisms against browsers may produce more seeds than those that have no defence mechanisms. In the absence of herbivores, defence mechanisms are useless costs and natural selection will operate against such costs.

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I’m in a bit of a rush, and so I can’t explain it very well at the moment.

One thing to remember is that people like good stories. A joke is don’t let facts get in the way of a good story. If a documentary is just a series of facts, it could lose the interest of people and so we will employee various storytelling techniques to get our message across. Just like how in the Bible they use language that says “ god came down from heaven “ when we know heaven is not actually up above us in the clouds.

Anyways as you know evolution according to many is not designed. It’s through natural selection. One process of natural selection is mutations. Mutations can often be good. We can see this is the coevolution of plants and their hosts. With plants it’s never just one single thing that is changing. At the same time leaves are developing different chemical compounds that are bitter and toxic to most insects, it can also develop thicker leaves and things like thorns.

So most likely at some point a plant developed bumps on it. These limbs were enough that it kept some animals from enjoying chewing the foliage. It was just slightly tougher in texture than the plant next to it. This allowed it to carry its fruit to term more often. Over time, as the only plants in this species developed bumps, and pollinated one another, the gene that caused the bumps were increased more and more often. Then some of those had a sharper bump that worked a little better. As that then begin to dominate it some would come a little sharper and longer. Over roughly 150 million years or so these angiosperms in this species have simply kept pollinating one another and that trait became more and more defined. Same way we saw the beaks of some birds develop longer and longer.

Thorns drive away larger mammals because they tend to have larger mouths and can pluck a single berry from the thorny stems. They chew big clumps of leaves and soft stems. So these thorns hurt and they eat less of it. Usually when these animals eat fruits and foliage, the seeds can be much larger, and they go through the digestive track and will have tougher outer layers dissolved off.

So while those thorns drove them away, smaller mammals and birds that could pluck just the berry would coevolve. When birds pluck these smaller fruits with smaller seeds, normally with thinner membranes around the seed, it does not need a long time in a digestive tract to break the tougher parts that make germination harder. Their beaks, and little claws, and smaller bites will scrape away ( scarification ) these outer layers. Some of these seeds may do better getting popped out in smaller shady spots. The little rodents often eat poop underneath foliage which means lots of shade. Larger animals will just poop in bright sun. Or maybe some of the seeds went through scarification by birds and got dropped far and wide and by chance some landed in good spots.

But these same seeds may not do good in a larger mammals digestive tract. It may be too strong and break down the seed to far. Or the poop may be composed of too much nitrogen.

For whatever reasons, coevolution resulted in niches where some thorny bushes had better chances of germinating through their interaction with the way birds or small mammals ate it.

Episodes 175 ( plant defenses ) and 195 ( leaves ) of the podcast “ A Common Descent “ should touch up on this subject a bit. Keywords to google would just be coevolution. That’s the evolutionary track of two separate species and the way their interactions influenced one another.


Human psychology is biased towards teleology and anthropomorphizing, so it is rather easy for us to invoke these ideas without realizing it. For example, why do we get mad at our cars if they break down?

Scientists are just as susceptible to these biases as anyone else, so it isn’t surprising to see anthropomorphizing in scientific explanations.

The explanation I have seen is that raspberry bushes with thorns were selected for because they shifted the species that eat the berries towards spreaders (e.g. birds) and burrowers. It also increased the number of animals that ate the berries which increases spread. 20 mice will spread the seeds better than the droppings of one deer.

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‘why do we get mad at our cars if they break down?’

because my name is Basil Fawlty.

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And then YECs pounce and claim scientists think that genes can think.

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