I recently encountered a fruit I’d never seen or heard of before: the finger-sop (Meiogyne cylindrica), native to Australia. The thing about the fruit that instantly impressed me was how much it resembled our native North American pawpaws (Asimina species), with one striking difference – instead of a greenish-yellow skin, the skin of finger-sop is bright red. Both fruits are obscure members of one of the ‘royal families’ of tropical fruit, the Annonaceae, which includes such famous delicacies as cherimoya, guanabana, and rollinia. But unlike those relatively recently evolved, glitzy, glamorous fruit superstars, the humble pawpaw and finger-sop appear to retain some of the ancestral characteristics of this fruit family, characteristics which reach way back in time.
Not only is the external appearance of pawpaw and finger-sop similar (aside from the color), the internal appearance is nearly identical, including the arrangement of seeds in the creamy flesh. And so is the flavor: finger-sop has that same mildly sweet, fruity taste, with a creamy texture and distinctive ‘pawpaw’ sort of flavor. The resemblance between the two is so close that if you blindfolded me and handed me a finger-sop fruit to eat without telling me what it was, I’d probably say, “I know this fruit, it’s one of our native Florida pawpaws.”
Since these two fruits share a common ancestor, the simplest explanation for the similar characteristics is that they both retain those characteristics from a common ancestor. So when did that ancestral fruit tree live, producing its oblong, sweet, pawpaw-like fruits? Scientists studying molecular clock analysis have found an answer: the last time these fruits shared a common ancestor was not a million years ago, not ten million years ago, but a whopping 71 million years ago. This is an ancient, ancient fruit type.
In fact, 71 million years ago is a particularly interesting number, because of another date: the time when the giant asteroid impact killed off the dinosaurs, which was 66 million years ago. This means that if the number produced by the molecular clock analysis is accurate, then for about five million years, trees producing pawpaw-like fruits shared the planet… with dinosaurs.
Did dinosaurs eat those ancestral pawpaws? The reason plants make fruits is to entice animals to eat them, in order to disperse the seeds. Dinosaurs were the dominant land animals at that time, filling ecological niches in size ranges all the way from the familiar mega-giant beasts, all the way down to tiny dinosaurs the size of a chicken. Even if the fruits evolved to appeal to some other animal as their main seed dispersal agent, it seems a virtual certainty that over the long span of five million years, hungry dinosaurs would have at least occasionally gobbled down a few of these pawpaw-like fruits. But since dinosaurs were so overwhelmingly dominant, it’s perhaps even more likely that these fruits co-evolved to entice dinosaurs themselves as their main seed dispersal agent.
So there you go. When you eat a pawpaw, you are partaking of a very long tradition, sharing a fruit experience that’s been enjoyed by 71 million years of creatures, including a very different type of biped, which held these fruits in its scaly hands a very, very long time ago.
One of the big questions I had was: how did these two kinds of fruit get to the opposite sides of the earth, Australia and North America? One possibility is bird dispersal. Some fruits can spread across oceans by birds carrying their seeds in their bellies, and dropping the seeds in faraway lands. But fruits adapted to being eaten by flying birds usually have much smaller seeds and fruits than either pawpaw or fingersop – these fruits appear adapted to be eaten by larger, heavier creatures.
So the ancestral fruit species probably would have had to cross over a land connection. I looked up the history of when the drifting continents were attached to each other to try to see if there was a land connection that would have existed between North America and Australia around 71 million years ago, either all at once, or in a successive series of land connections that would have allowed a plant species to spread between these two land masses. I was hoping to find fairly precise dates for when land connections between continents formed and severed, to really nail down the story of these fruits. But I found that while scientists are fairly confident about what the general pattern of continental drift has been, they have a lot more uncertainty about exact times of when land connections formed and broke apart.
I did find one intriguing thing: there’s at least some evidence that between 75 and 65 million years ago, the continents of North America, South America, Antarctica, and Australia may have been linked in one long chain which would have allowed the spread of species all the way across. That fits our timeline perfectly. If that’s true and if that’s how the ancestors of these fruits spread, it’s interesting that a crucial link in that chain would have been Antarctica, which sat over the South Pole then as it does now, but which was densely forested. The Earth was much warmer in the late Mesozoic than it is now.
Although pawpaw and finger-sop are very similar fruits, they have one striking difference: ripe pawpaws are greenish yellow, but ripe finger-sops are bright red. Is there a way to guess which if either of those color patterns the ancestral fruit may have had?
We can make some speculative guesses, based on which kind of animals the fruits seem to be evolved to attract as their seed dispersal partners.
Pawpaws show all the classic features of a mammal fruit. Since most mammals have poor color vision and can’t see the color red at all, fruits adapted to mammals often ripen to a green or dull yellowish color. Mammals generally have an excellent sense of smell, however, so a common trait of mammal fruits is to announce their ripening to mammals by becoming fragrant. Pawpaws do develop a pleasant fruity fragrance upon ripening, but their color hardly changes at all from a solid green in the unripe stage, to a slightly greenish-yellow when ripe.
Finger-sops, on the other hand, turn from green to bright red when they ripen. Among mammals, only some primates and possibly some marsupials can see the color red. Australia obviously has lots of marsupial mammals. Birds can see the color red very well, and Australia is home to cassowaries, large ground-dwelling birds that eat mostly fruit. Australia was until recently also home to giant tortoises, which also can see the color red very well.
There’s another category of animals that are thought to have had excellent color vision, including the color red: dinosaurs. So if our guess is correct that dinosaurs where the seed dispersal agent that the ancestral pawpaws co-evolved with, then it’s quite possible that those ancestral fruits resembled finger-sops, announcing their ripening to hungry dinosaurs by turning bright red. We may have to update our vision of late Mesozoic forests to include dinosaurs traipsing through forests in search of the flashes of bright red that indicated a tree full of sweet, pawpaw-like fruits for them to eat.
#Annonaceae #Asimina #Asiminaparviflora #Meiogyne #paleopomology
Florida Fruit Geek 
This is just a fun, speculative look at some possibilities for the ancestry of these fruits. My whole idea about the ancestral fruit co-existing with dinosaurs is based on the chart on page 669 of the work I linked to in the text. If you look at the chart, it’s clear that the Annonaceae family and its genetic relationships are really complicated. There over a hundred genera in this family. To really get an idea of what the ancestral Mesozoic representatives of this family might have looked like, it would really be necessary to analyze the characteristics of all these genera, not just two of them, as I have done. But if the molecular dating numbers are accurate, it does appear that the ancestor of pawpaw and finger-sop lived in the late Cretaceous alongside dinosaurs, and likely had much of the eating characteristics which those fruits share today. I love that!
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Hi,
My name is John. I have a nursery in Quincy, Florida. I have a keen interest in fruit growing. Do you have seeds or seedlings of that Australian fruit? I’d like to speak with you if possible. Great Work!
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Hi John, thanks for commenting! I only had a few seeds, I planted them and I’m still waiting for anything to come up. Probably best for you to contact the person I got the fruits from, Larry Shatzer of Our Kids Tropicals in Winter Garden. He’s got a big, fruiting-size finger-sop tree in a pot. I was there just a few days ago, and there were still some green fruits on the tree. Larry can probably send you some ripe fruits whenever they mature. He might also have some seedlings available.
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Interesting fruit. Do you know how hardy it is or in which areas of Australia it grows natively? There is almost no information available online.
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I don’t know what part of Australia it’s from. My friend has a tree growing in Orlando in Central Florida, and his tree was exposed to temperatures near and possibly slightly below the freezing point. The partially defoliated and had minor twig damage, but it’s since leafed out again and looks healthy.
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Actually… the closest thing to a dinosaur that may have dined on this fruit is Gastornis. 77 million years ago, dinosaurs were already birds. This fruit existed during the Paleogene period. Gastornis is best imagined as a primitive parrot in appearance, though it is not related to any present day birds. It was a forest dweller and fossils have been found in France, Belgium, Germany and North America. It was also a flightless bird with small wings, so it is very likely that it dined on insects AND fruit. But another theory suggests it was well equipped to hunt and eat Hyracotheum, a very early ancestor of the Rhinoceros and the Horse which was the size of a small dog. The first fossil was discovered in France in 1855. It also had very large feet (16 inches long in one case and in another the feet were 11 inches wide and 13 inches long). Gastornis could grow to be up to 7 feet tall.
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Hi Ceratopsian, thanks for commenting! Great info about Gastornis – I had previously been aware of it as the carnivorous Diatryma, and I just learned that it’s been re-classified as Gastornis. And it’s news to me that it’s now considered to have likely been an herbivore, so it’s definitely a possible seed dispersal agent for fruits during the Paleocene and Eocene.
The “dinosaur” line of reasoning that I used in this blog post all revolves around the molecular clock divergence date of 71 million years ago, during the Cretaceous. Since the extinction of non-avian dinosaurs occurred 66 million years ago, that means that for about the last five million years of the Cretaceous period, a tree with fruits like these shared the planet not only with birds, but also with non-avian dinosaurs, which were the overwhelmingly dominant category of land animal at the time.
(Of course, this is based on the accuracy of that molecular clock divergence date). Since Gastornis fossils haven’t been found from before the Paleocene, it’s conceivable that this fruit was dispersed by avian and/or non-avian dinosaurs during the late Cretaceous, and by terrestrial avian dinosaurs like Gastornis subsequently during the Paleocene and Eocene. And probably by a changing cast of characters ever since.
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I have written a couple articles on this subject. Here is a summary/teaser:
We can still see the influence of giant dinosaurs on their plant symbiots. Just look at the giant fruits that some plant species occasionally produce. Consider the 20,000-calorie Jackfruits, and 10,000-calorie durian fruits that we occasionally see growing high up on trees in equatorial regions. These are not random mutants, but random throw-backs. They are plant genomes randomly trying an approach that worked for some 140-million years. They are relics and evidence of a time when most tall trees produced macro-fruit to feed the biggest, highest-reaching, and hence the best seed spreaders at the time, a time before birds had evolved.
The biggest sauropods are supposed to have had a mass up to 35 times that of African elephants today. How did they eat enough leaves with their tiny heads and mouths? And how did they even strip enough leaves with their small front-of-the-mouth “pencil teeth” like diplodocus had? On the other hand, the small heads and pencil teeth make complete sense if the sauropods were being selected for their ability to reach and pluck the highest macro-fruit — fruit almost universally on break-away stems.
And what is fruit, but the highly nutritious part of a plant that has evolved to attract animals that will spread the plant’s seeds? And why should we say that dinosaurs were not eating fruit, when most herbivorous reptiles (and elephants) prefer rich fruit to leaves?
Here is a new unified theory of tetrapod evolution. It follows “the money”, the nutrition to explain how:
1) The network dynamics of seed spreading caused most major events in tetrapod evolution.
2) The advantage of animal seed spreading nourished and pulled vertibrate life out of the oceans.
3) Larger animals were better seed spreaders, and how this network effect caused dinosaur gigantism.
4) Once Birds became more efficient seed spreaders, they reversed the evolutionary network effect that gave rise to dinosaurs, thus eventually ending dinosaur gigantism.
The full new theory is at: http://www.AndrewMelcher.com
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Hi Andrew, thanks for commenting. I love discussions of seed dispersal and how it’s influenced animal evolution, such a fascinating topic. I’m going to spend some time reading your website, sounds like you’ve done a lot of research and thinking about this.
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Fantastic information! What eats fingersop and pawpaw in nature today besides us. Possums? I believe both continents share the mammal.
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There are lots of the smaller-fruited pawpaw species in my area in North Florida (especially Asimina parviflora), and when their fruits ripen and drop to the ground, they disappear quickly. I assume it’s mammals eating them, most likely the numerous possums and raccoons around here. The larger-fruited pawpaw species that grows further north (Asimina triloba) might have evolved to suit the tastes of some of the larger mammals that went extinct in North America 12,000 years ago, like mammoths and giant ground sloths. My understanding is that the mammals called “possums” in Australia are only distantly related to the North American mammals of the same name, although both are marsupials. Possibly it might be the giant, flightless, fruit-eating cassowary birds that are eating fingersop fruits in Australia, since they can see the color red, and those fruits are colored bright red.
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