20,000—calorie jack-fruits . . . and long dinosaur necks to reach them

The record jackfruit weighed 45-kilos and had over 25,000 calories.

Today we occasionally see 20,000-calorie Jackfruits, 10,000-calorie durian fruits, and one-ton pumpkins with over 260,000-calories of nutrition. And dozens of other plant species occasionally have individual trees producing giant fruits high up above the ground, fruits that are hundreds of times larger than necessary to spread their seeds.  Why are so many plant species occasionally squandering these huge amounts of energy?

There is no explanation for all this recessive fruit gigantism in today’s world. But it does fit well with dinosaur gigantism. So here we imagine a world before birds, where many trees and vines bore giant fruits that interested giant sauropods (like brontosaurus). These trees evolved to have giant fruit up high, and thus the giant fruits tended to only be eaten by the biggest animals capable of reaching them. These were animals so big they had to constantly rove in search of food.  And at this time (before birds evolved), this was the best way for trees to disperse their seeds far away.

At this time, the plants that did not provide giant and costly meals to the sauropods had to rely on ineffective means like the wind and insects and small animals for seed dispersal. Thus the macro-fruit trees were best able to spread into the new habit zones constantly created by climate change, storms, and forest fires. Thus it was seed dispersal that caused the era of dinosaur gigantism on earth.

At the same time, or shortly after, small reptiles were being selected for their ability to climb up straighter and straighter trees, until they could climb up vertical trees and reach the macro-fruit feeding the macro-animals.  This caused fruit trees to develop countermeasures against the small animals trying to cheat their hugely costly and hugely important spreading system.  Here is why most fruits have  bitter and hard to penetrate skins, and more importantly, why nearly all fruit evolved to dangle on break-away stems.  

The break-away stems were a “killer” adaptation as there were only two ways for animals to deal with the deadly break-away dangling fruit.  One way was to glide to the ground safely, and this is what caused the birds to evolve. The other way was to become so small, that they would not cause the fruit to break away: and also so inconsequential, that one Jackfruit would feed a number of their kind for all their short lives. This second way is what caused the mammals to evolve.  

Eventually the birds became better and less costly seed spreaders than dinosaurs. Then energy efficiency and natural selection started favoring the trees that catered to the tiny birds with much smaller fruit and seeds. Then over a long period of time, many fruiting plants started catering to bird sized appetites instead of the massive dinosaurs and their costly appetites.  Then with less and less fruits to eat, there were fewer and fewer giant dinosaurs. Then ultimately, there was a big climate shock that killed all the remaining dinosaurs.

An 8-kilo durian will have over 10,000 calories of nutrition.

Again, fruits like the durian above were once in the treetops, where only the biggest, farthest-roaming , longest-necked dinosaurs could reach.  Before birds evolved, catering to the biggest dinosaurs was the only way for trees to spread their seeds far away.

Now it is widely accepted that plants give animals a snack of fruit in order to spread their seeds. But what about macro-fruits like the 10,000-calorie durians we occasionally see?  These are much more than a snack for any animal living today,  and dozens of plant species occasionally produce giant individual fruits.

Throwbacks, not mutants
These giant fruits are not mutants but throwbacks. They are the plant genomes (many plant genomes) randomly trying an approach that worked for about 140-million years.  And taken together, the widespread existence of these super-costly macro-fruits in so many plant species tell us that macro-fruits were once normal on our planet.

An iguana eating fruit whole

Prosauropods and gymnosperms
The giant fruit, high up on trees, co-evolved with the giant reptiles.  In fact, the rise of the sauropods, including the earlier prosauropods came along with the rise of the  angiosperm plants (the flowering and fruiting plants) the seed and fruit bearing plants. This is because both were evolving as symbiots.

Here is a durian tree heavy with fruit for long extinct sauropod symbiots. Here is maybe 50,000 or 100,000 calories of nutrition on half a semi-mature durian tree. What else but giant long-necked sauropod dinosaurs could have been eating this spine covered, impenetrable fruit high up on a tree?

If these papaya plants mature, the massive nutrition of their fruit might be over 10 meters up. What sort of giant animals did this plant evolve this crazy over-supply of nutrition to feed?

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Durian fruit is as caloric as meat
Durian has about 1,470 calories per kilo.  This is roughly the same caloric content as raw beef tenderloin (1,480) and whole turkey (1,410).  And it is much more than raw tuna (1,050), raw skinless chicken breast (1,140),  and bananas (950).  So an 8-kilo Montong durian, might have 10,000 calories, about the same caloric content as a 8-kilo turkey.  Now mature durian trees will each have dozens of these fruits hanging from them. So a grove of durian trees will have a vast amount of energy to feed roaming dinosaurs.

Seed spreading is key to tree survival
For trees in a forest, the first mover advantage has always been quite important. The first tree to spread its seeds gave a big advantage to its offspring. They get nearly all the light, and they leave little light for later competitors. So the first mover (or seed spreader) generally won the race. Also having several avocado-pit sized durian seeds spread in a large piles of dinosaur dung fertilizer surely must have helped a great deal.

Seed dispersal and habitat enlargement was the reward for trees species that could please and sustain their giant animal symbiots. These species prospered over the other species during the era of dinosaur gigantism. And again, this was before the advent of birds, so at this time, getting eaten by a huge dinosaur was the best way to for trees to spread their seeds.


Today most macro-fruits grow closer to the ground, but during the age of the giant sauropods, they would have grown quite far above the ground.   Also, if the sauropods were creatures that evolved to reach food high up in trees, this key aspect of their existence would be better shown in one of the two positions below.

To start, the sauropod is reared up almost vertically on his hind legs and mounted to a tree.  This is to maximize its reach.  The thumb claws on its front limbs are digging into the soft bark of the tree and stabilizing the tall and unstable animal. The animal’s neck might even spiral the trunk of the tree a bit, for added stability.  Later, if there was no need to reach high, the animal would rest it’s heavy back-half on the ground and feed on lower branches.

The fruit got higher and the necks longer
The sauropods (like brontosaurus) were the group of reptiles specialized in reaching and eating the macro-fruit of the tallest trees. Early on, (around 225-mya) these developed longer necks (like with the prosauropod Plateosaur below). The sauropods developed long necks because that was a more efficient way to reach the fruit.

The earlier plateosaurs were up to 10-meters long.

The twistable thumb claw
At some point the prosauropods developed the twistable thumb claw (below). This enabled the long and unstable dinosaur to stand up on its hind legs and grasp a tree for support, and stability.

In sauropod trackways, the thumb claw is not seen. It is widely held that sauropods held their thumbs up when they walked. So it is easy to imagine that the thumb claw was critically important to rearing up, getting the macro-fruit, and surviving.  To prevent damage, the thumb claw was held up when the sauropods lumbered between fruit trees.  And just as the thumb claw could be held up it probably also could be lowered, or pressed down into a trees soft bark.


Here we see thousands of calories of dates high up on a date palm tree.  Why is this plant squandering all this energy?  Unless we accept that the plant evolved all this costly fruit to feed giant seed spreading symbiots, the giant amounts of fruit nutrition make no sense.

Dinosaurs were dying-out before the climate shock
The important thing to note in the above graph is the way the extinction rate was already increasing/spiking before the climate shock. From the start of the Jurassic era, it seems that the macro-fruit trees suffered from constant attacks on their fruit bribes from countless varieties of miniature cheating animals. This caused many species to start going extinct at an accelerating rate starting around 90-million years ago. Then, 66-million years ago, there was a climate shock that finished off the remaining dinosaurs

Macro-fruit was for sauropods
The macro-fruit trees didn’t need any small animals climbing up and cheating the system, eating their precious fruit bribes and doing nothing to help spread their seeds. So evolution favored the plants that put their fruit up high, really high up, where only the biggest animals could reach. And evolution also favored the plants that had fruit with thick rinds, thorns and slow digesting fruit, as well as other counter-measures.

So before birds, plants needed to get tall, so that they could put their seeds and fruits high up. This was so only the biggest eternally roving animals would eat their seeds and spread them as far as possible. And at the same time, the sauropods, the main symbiots of these tall trees also evolved towards size and high reach. And in this pre-bird ecosystem, high reach mattered above all else. Speed, intelligence, metabolism and endurance did not matter. During the age of dinosaurs, the animals (sauropods) needed to get huge and tall to reach the big fruits, and thereby get enough energy to survive and reproduce.  And again, it was an ecosystem that was primarily based on size and high-reach, and these characteristics above all others. 

However, once the birds became better seed spreaders than the dinosaurs, there was no need for the plant to invest energy in producing macro-fruit.  And once there was not much macro-fruit, there was little need for the animal to invest energy in the growing huge. So over millions of years one plant species after another stopped producing macro-fruit, and started producing today’s bird-sized fruits.

How gliding and expendable individuals
short-circuited dinosaur gigantism
Once the gliders (proto-birds) evolved to a point, the rules of the game changed. Nature no longer favored size because fliers (birds) were even better seed dispersers than dinosaurs and they cost less than 1% as much energy to feed.  So on the plant side of the symbiosis, the costly system based on hugely “expensive” durian-scale bribes began to collapse under its own extreme “cost”, and in species after species, trees started producing smaller fruits to feed the smaller flyers.

In other words, the trees that produced more bird-sized or rat-sized fruit leapt ahead of the trees that wasted huge amounts of energy producing 10,000 calorie durians. Then over time, the nature of our planet’s forests changed. And eventually, over millions of years, the planet’s trees all mostly stopped giving huge amounts of energy to macro-creatures, and macroism died out in favor of smaller seeds, smaller fruits and flight and high metabolism. And today we have to consider thousands of individuals to find one macro-fruit bearing tree.

Giant mutant fruit
It is worth repeating, that the giant “mutant” fruits we occasionally see today — the 700-kilo pumpkins and 4-foot-long papayas — are not mutants at all, but throwbacks. They are legacy dinosaur fruit varieties that many of plant genomes randomly try again from time to time. In some cases, the throw-back mutant is cultivated by man, but mostly all the huge dinosaur-sized fruits have now evolved to be today’s “normal sized” or bird size for today’s flight-enabled ecosystems.

Here some giant “throwback” passion fruit about 20x “normal” volume.  A great many fruiting plants (especially tropical plants) occasionally produce much larger fruits of the old dinosaur size.

Dinosaurs a concise natural history, Fastovsky Ch.8
“In all sauropodo-morphs, the gut must have been capacious… Sauropods likely had an exceptionally large fermentation chamber (or chambers) that would have housed endo-symbiots; that is, bacterial that lived within the gut of the dinosaur. The endo-symbiots would have chemically broken down the cell walls of the plant food, thereby liberating whatever nutrition was to be had. Considering the size of the abdominal cavity in sauropodo-morphs, these animals probably fed on foliage with high fiber content. Perhaps they also had low rates of passage of food through the gut in order to ensure a high level of nutrient extraction from such low-quality food. We can only conclude that these huge animals, with their comparatively small mouths, must have been constant feeders to acquire enough nutrition to maintain themselves. The digestive tract of a sauropod had to have been a non-stop, if low-speed conveyor belt.”

Fragrant durians
In some places they don’t even allow un-opened durians in taxis and on transit due to their extremely strong smell. And Jackfruits, mangos, and passion fruits are also quite fragrant.  And we humans have a terribly weak sense of smell, and we can easily smell an open durian 100 meters away. So it is not hard to imagine that a stand of durian trees might have called its animal symbiots from perhaps a kilometer or two away. And it is not hard to imagine that the giant lumbering sauropods were pausing every couple hours to relieve themselves. After all, nature would have favored the individuals that would better spread the seeds that would grow the trees that would produce the food that their offspring would live off of.

Fruit-eating reptiles today
How do fruit-eating reptiles eat peas, edamame, lima beans, petai, carob, or small cocoa pods that are suspended from above? Do they ever nibble the seeds out of their casings? And if we line up durian, avocado, carob, cocoa fruit, and other suspected macro-fruit, what does each species eat first? And which macro-fruits will carnivorous animals eat?

How do you feed a 50-ton dinosaur on leaves?
This is about the weight of 8 African bush elephants, which actually prefer fruit and eat a quite a large amount of fruit. How do you get that volume of leaves through the tiny head and mouths that sauropods have?

Giant stretch-lizards
Clearly the sauropods evolved to reach something up high.  Was that leaves, or fruit, or both?

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