What's a better choice: Treif meat or human flesh?

Question

If one is stuck on a deserted island with no kosher food and he has a choice between eating human flesh of a dead person or the flesh of a non-kosher animal, which is preferable to eat?

Answer 1

To add to mevaqesh's answer:

R/Dr Alan Brill (Edah Journal, "Worlds Destroyed, Worlds Rebuilt: The Religious Thought of Rabbi Yehudah Amital") retells "two stories of moral challenges told in Yeshivat Har Etzion circles that contrast R. Amital with his co-Rosh Yeshiva R. [Aharon] Lichtenstein." The first story is also relevant to the broader question, but the second case is this one exactly.

To quote:

The second story concerns the scenario where one is in an extreme situation and has this choice: whether to either eat human flesh or pork. The standard halakhah designates pork as a biblical prohibition and human flesh as only a rabbinic prohibition (assuming the flesh is already dead and there is no question of murder); hence one should eat the human flesh. R. Lichtenstein is wont to go further and consistently point out that the punishment for the consumption of pork is only lashes while eating fruits from the priestly portion that has not been taken is excision (karet). In contrast, R. Amital almost shouts out from his soul that human flesh should be repulsive to everyone's natural sense of morality so that one should eat the pork, and the reason that the prohibition was not stated in the Torah was because this revulsion is a natural intuition not needing to be stated. R. Amital also adds a more halakhic reason that the calculation of choosing to violate a rabbinic prohibition over a biblical one is itself only rabbinic.

He further cites as a paradigm for his thought the famous statement of Rabbi Moses Samuel Glasner (1856-1924) in his Introduction to Hullin...

... for which you should see mevaqesh's answer.

In the version I first heard, R Amital concluded that he assumes that in practice both would eat the pork. The difference is R' Lichtenstein would afterward feel he did something wrong.

But, as R/Dr Brill stays in closing his discussion of the case:

R. Amital guards himself in the halakhic realm by noting that some say R. Glazer went too far—and may not be correct as halakhah. However, for R. Amital, R. Glazer’s approach can still serve as our paradigm of ethics and as a rejection of legal formalism by affirming mandates outside of texts (page 40). Once again we are left without criteria about when to rely on this moral sense; rather, R. Amital asks the important questions of the moral dilemmas of collateral damage, triage, and wartime ethics, but he does not give answers. R. Amital’s consistent reliance on moral sense exemplifies his commitment to the idea that we should be trained to think for ourselves and figure out the needed and correct response in these difficult situations.

Answer 2

Rabbi Moshe Shemuel Glasner (1856-1924) writes in the introduction of his Dor HaRevi'i to Chullin Pesicha Kolleles § 2 s.v עוד משל אחת that if one has the option to consume human flesh or non-kosher meat, even though the former is at most prohibited by a positive commandment, while the latter is prohibited by a more stringent negative commandment, it is preferable to consume the animal flesh. This stems from meta-halachic concerns which he discusses there at length. The primary issue is that cannibalism is something which ought to be repulsive to us even sans technicalities, and is to be avoided even at the expense of the prohibition of forbidden meat:

כל מה שנתקבל בעיני בני אדם הנאורים לתועבה, אפילו אינו מפורש בתורה לאיסור, העובר על זה גרע מן העובר על חוקי התורה . . . ועתה אמור נא, בחולה שיש בו סכנה ולפניו בשר בהמה נחורה או טרפה ובשר אדם, איזה בשר יאכל, הכי נאמר דיאכל בשר אדם שאין בו איסור תורה אע"פ שמחוק הנימוס שמקובל מכלל האנושי, כל האוכל או מאכיל בשר אדם מודח מלהיות נמנה בין האישים, ולא יאכל בשר שהתורה אסרו בלאו, היעלה על הדעת שאנו עם הנבחר עם חכם ונבון נעבור על חוק הנימוס כזה להינצל מאיסור תורה? אתמהה! ‏

Answer 3

So we will now analyze the order of which comes first human or treif animal Flesh .

Rambam Hilchos maacholos asuros 2,3:

האדם אע"פ שנאמר בו ויהי האדם לנפש חיה אינו מכלל מיני חיה בעלת פרסה לפיכך אינו בלא תעשה. והאוכל מבשר האדם או מחלבו בין מן החי בין מן המת אינו לוקה. אבל אסור הוא בעשה שהרי מנה הכתוב שבעת מיני חיה ואמר בהן זאת החיה אשר תאכלו הא כל שהוא חוץ מהן לא תאכלו ולאו הבא מכלל עשה עשה:
A Man even though referred to as a "Chaya" is not included in the category of chaya which the Torah enlists with regards to kosher/nonkosher animals. Someone who eats meat from a human or the fats whether taken from someone live or dead does not get lashes. But its still forbiddon to eat as it says "These are the animals which you should eat, which implies an exclusion to humans which are not in the category of "chaya." Therefore there is a prohibition implied from a permission which is a mitzvas asei.

Maggid Mishna:

וזה דעת הרמב"ן ז"ל והרשב"א ז"ל שאין בבשר האדם איסור כלל מן התורה אלא שהרמב"ן ז"ל כתב שהישראל שמת בשרו אסור אף בהנאה מן התורה וכבר נתבאר דין איסור ההנאה של מת בדברי רבינו פי"ד מהלכות אבל.
The Ramban and Rashba say with regards to such meat there is no prohibition from the Torah whatsoever, but with a dead jewish corpse one cannot have benifit from it

The Mishne Lemelech Hilchos aveilus 14,21 says about benefiting from a dead body

אסור בהנאה משום דאתיא שם שם מעגלה ערופה והיא הלכה פסוקה כתבוה כל הפוסקים ז"ל ובכל איסורי הנאה המכירה היא אסורה מדין תורה דהא איצטריך הכתוב להתיר נבלה בהנאה - It is forbidden to have benefit from the dead body from the Torah as we learn from Egla arupha to Miriams body a Gezeira shava "Shom Shom" unanimously agreed from all the Poskim and this includes selling the body.
He continues later on:תשובת הרשב"א סימן שס"ה שהשואל היה סבור דג"ש זו לא נאמרה אלא במתי ישראל ועל זה השיב דאי איכא מת דלא מיתסר בהנאה יין נסך דאסור בהנאה מנא לן דאי משום דאיתקש לזבח וזבח איתקש למת ההוא מת גופיה מנא לן דמתי ישראל קאמר ע"כ הרי דס"ל להרשב"א דאף מת עכו"ם אסור בהנאה - basically not only a Jewish body but also a gentile body is Ossur Behanaa (prohibited to have benefit) Mideoraisa (from the torah) and this is the opinion of the Rashba Ramban and Rambam(aveil 14 21 see radvaz).

To explain the Rambam that says there is only a asei for eating a human and no prohibition or Issur hanaa the mishne Lemelech brings the Rashba that concludes רשב"א ריש סימן שס"ד שכתב אבל לפי דעתי יהיה זה בבשר מן החי אבל המת למדו בו ג"ש מעגלה ערופה , this halacha -that there is only an asei on eating the meat- applies to meat from a live human i.e a limb fell off. But a dead man has a prohibition (Lo taaseh) that is even forbidon for benefit from Egla arufa which is in turn derived from Kodshim as it says in Sanhedrin 29b: כתיב הכא (במדבר כ, א) ותמת שם מרים וכתיב התם (דברים כא, ד) וערפו שם את העגלה בנחל מה להלן אסור בהנאה אף כאן נמי אסור בהנאה והתם מנלן אמרי דבי רבי ינאי כפרה כתיב בה כקדשים: and Kodshim is prohibited with a Lo taase of וזר לא יאכל כי קדש הם (shemos 29,33)

In summary if your in the dessert with a live guy who's limb fell off, a dog, a dead man (regardless of his religion) and loads of ants (they even live in the dessert) and it is pikuach nefesh to eat, according to the above This is the order:
1.The limb from a live man,(Rambam-asei deoraisa)(Rosh-ossur derabanan)(Ramban-muttar)
2.The dog which is prohibited to eat but permissable to benefit from,(Lo taasee)
3.The dead human which is a even prohibited Biblically to benefit from,(Rambam-lo saase & asei)(Ramban Lo taase)
4.The ants for which each one is chayav 5 lo saasehs (see makos 13b).

Note:The halacha does not follow rabbi Glasner who says the worst thing is to eat human flesh as the Rashbash siman 518 quotes the baalei Tosfos saying that their was a Minhag for the mother of the child to eat the Orla forskin that was cut of during the Mila. This was not pikuach nefesh and yet permitted by the Baalei tosfos lechatchila. This ruling against Hagaon Harav Glasner is confirmed by Hagaon Harav Aharon Lichtenshtien Zatzal one of the 21st century poskimin in the quotation from Rabbi Dr Alan Brill cited in another answer.