(image source: airliners.net)
What are those humps on the rear of the wing? Are they external fuel tanks?
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4$\begingroup$ That's not a DC-8, it's a Convair 990,and those 'humps' are anti-shock bodies. $\endgroup$– CatchAsCatchCanCommented Oct 29, 2022 at 5:42
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You are looking at a Convair 990 Coronado and not a Douglas DC-8 aircraft.
For a direct comparison look at the image below. The Convair 990 has, compared to the DC-8, more windows that are more closely spaced. Also, when you look at the cockpit windows, the DC-8 has eye-brow windows while the Convair 990 lacks them. In the image you posted you can clearly see the distinct trapezoidal entry doors (wider at the top than at the bottom) of the Convair while the DC-8 has the usual rectangular doors. The most obvious difference are the "humps" on the wing of the Convair
Douglas DC-8 (left) and Convair 990 side by side (Source: Wikipedia)
The "humps", as you called them, are anti-shock bodies designed to reduce wave drag when traveling in the transsonic speed regime. The idea behind it is to keep the cross section constant over the length of the aircraft and smooth out cross section area changes. This is known as the application of the area rule.
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1$\begingroup$ Weren't they called 'speed bodies' in Convair publicity? $\endgroup$ Commented Oct 30, 2022 at 16:15
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1$\begingroup$ @MichaelHarvey I'm not aware of the nomenclature Convair used in their public relations material. The anti-shock bodies are also known as Whitcomb body, Küchemann carrot or speed bump. Richard T. Whitcomb (NASA) and Dietrich Küchemann (RAE) being the namesakes. $\endgroup$– ChrisCommented Nov 1, 2022 at 17:13
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1$\begingroup$ You forgot the most important difference: The DC8 smiles! $\endgroup$ Commented Nov 2, 2022 at 2:08
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1$\begingroup$ @RetiredATC I've never seen it like this – you're right! Not as broad as a B747F though. $\endgroup$– ChrisCommented Nov 5, 2022 at 12:12