Can I just say: that’s pretty rad.
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How does this tell us anything at all about where the narrowest point is? To give an obvious example, if I applied this technique to the radiation symbol l would conclude that the narrowest point is in the south, despite the fact that the narrowest point is clearly in in the dead centre.
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How do you define where a continent ends? Does Africa end at Israel, or at Turkey? Does North America end at Mexico, or at Colombia? As noted above, where you draw your arbitrary demarcation line totally changes where your north-south midpoint lies. There is no objective reason why the Central American isthmus is considered part of North America. Biologically, geologically and culturally it has more in common with South America. The same applies to the Arabian Peninsula wrt Africa cf. Asia/Europe.
How did that become the question? The OP was about continents being “bigger at the top” not about where their narrowest point was. I think having more area is the most reasonable definition of “bigger”. And as I wrote, north and south are not arbitrary conventions, so “at the top” also has an objective basis.
I don’t think anyone’s going to argue that Israel or Turkey are in Africa - they’re both Eurasian countries.
I figured that continents are geographic features not cultural ones. No point in being anthrocentric about it. So I figured the “border” between North and South America is along the Panamanian-Colombian border and the “border” between Africa and Eurasia runs along the shortest line between the Gulf of Suez and the Mediterranean. I also only counted the continental mainlands rather than including islands.
Actually, the reason continents taper to the south has a lot to do with plate tectonics.
Nearly every mountain range owes its origins to one (or both) of two phenomena: subduction of one plate beneath another, or collision of two continent-bearing plates.
Nearly every large peninsular area has a mountainous spine. (In a very few cases, e.g., the ridge underlying Florida’s east coast, these have been peneplainated and eroded down to something not recognizable as ‘mountainous’, but geomorphologically they do exist.)
Now, let’s address ‘continent’ from the geotectonic meaning, not the “common sense” geographic one. In this usage, Greenland is part of North America, as are the Kamchatka and Chukchi Peninsulas of Asia; the majority of Eurasia is a single continent, but India, Arabia, and “Burmalaysia” (Myanmar, Thailand, Indochina, the Malay Peninsula, and the ‘big islands’ of western Indonesia) are three other smaller ones that have collided with Eurasia.
So we have the following:
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North and South America and Antarctica are moving in unison in a direction we will refer to as ‘west’ because it is true for the Americas; defining it for Antarctica becomes an exercise in semantics, but if you look at a globe held so that Easter Island is approximately center of the visible hemisphere, you can see the continuation of the Cordilleran-Andean chain running down the Palmer Peninsula and the Transantarctic Mountains, marking the leading edge where the three continental plates are overriding the Pacific, Nazca, Cocos, and Farallon Plates. This results in upthrust on their west coasts and across ‘western’ Antarctica.
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Australia (which geotectonically includes New Guinea and Tasmania and most of New Zealand) is moving east and north, resulting in the main Australian range along the east coast, the spine of New Guinea running more or less east-west but continuing the Australian chain in a smooth arc, and New Zealand, squarely athwart the plate boundary, with a north-south alignment.
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Africa is principally moving north. But it is ‘sluggish’ in terms of speed of plate motion. It’s important to note that Iberia and Italy are broken-off pieces of Africa welded to Europe; hence the Alps, Pyrenees, and Atlas ranges. The grazing collision of the African and Indian plates combine with the incipient fracture in Africa along the Great Rift Valley to account for the discontinuous East African ranges.
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Arabia, formerly another piece of Africa, and India comprise two small plates that have collided with Eurasia and are being subducted beneath it. The results are to be seen in the Caucasus, the ranges of northern Iran, the Himalaya and its affiliates.
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What I referred to as “Burmalaysia” above is the result of a much older impact with Eurasia. Hence there are nearly no significant mountains along the suture joining it to China; instead, it is being impacted by the eastern edge of the Indian plate (which extends southeast underwater toward Australia, moving in so close lockstep with the Australian plate that there is still debate over whether it constitutes a single plate bearing both India and Australia). The result is the mountainous spine running in an arc from the Himalaya and its parallel ranges down the spine of the peninsula, continuing as Sumatra and Java.
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Kamchatka and the mountains of eastern Siberia result from the impact of the North American plate with the Eurasian plate.
So east-west ranges characterize geographical Eurasia, and north-south ones the other continents, pretty much in keeping with plate tectonic theory.
Yes, you’re right. I was being thrown off by the way the maps were drawn.
While the Americas and Aftrica definitely taper Southward, Australia looked that way because of the map. Having gotten a few continents that fit the pattern, I was essentially willing Eurasia into conforming to the theory and tossing out Antarctica altogether.
Some of you seemed to spend an inordinate amount of time reconstructing the question to prove me a fool rather than answering my curiosity.
I think you’re being overly sensitive. I’m not seeing a lot of snark in most answers here. If you ask a question like this, you have to expect that people are going to examine your premises. And you admit yourself that you now think that your premise was wrong.
I thought he was spot on. Arguments about Eurasia, Australia, and Antarctica seemed like valid questioning of the premise, but this thread saw seriously proposed arguments that Africa, N. America, and S. America don’t narrow as you go south. That seemed a lot more like completely attempting to redefine the premise.
People in this forum are quite capable of disputing the allegation that “the sky is blue.” 
Such arguments should not be taken as a personal affront .The remark that people were trying to “prove him a fool” was overly sensitive.
Do Not Taunt - It is perfectly legitimate to argue that the Africa, N. America, and S. America don’t narrow as you go south, or that the perception of such narrowing is completely dependent on perspective. North America, for example, appears to narrow in the west from some viewing angles.
I have no idea what you’re trying to show me with that picture. That if you redefine west to mean south, that North America narrows to the west?
No. From the north, North America looks like a wedge: a curved “bottom” from Maine to Baja California, and the sides narrowing to a “point” in Alaska.
I’m trying really hard to see what you’re saying, squinting even, but I just can’t get there. But I’m not sure I even get the meta-point: a continent can narrow on the east-west axis and also on the north-south axis, and I just don’t see a way to look at North America and see the northern part as being less or equally wide than the south. It’s clearly wider: the bulk of the land mass is in the northern half.
Again, it’s not an issue of “narrowing”. Any landmass obviously comes to a point. The issue is where the majority of its overall area is.
This must be the reason why there’s a continent around the South Pole, but not the North Pole.