Evolutionary Ethics: Contextualizing the Biblical Laws of War and Herem

War, or at least group fighting and killing, has been part of human society since the beginning.^[1] Ethnographic evidence from primitive societies shows that competition is particularly brutal when two tribes compete over territory: In these situations, competition becomes a zero-sum game in which each side seeks to annihilate its rival. This merciless attitude towards the out-group is often motivated primarily by fear of future retribution by one's enemy, since a miscalculation could lead to catastrophe for the in-group.

To choose a prehistoric example: Where are the Neanderthals, our genetic brothers, who parted ways from homo sapiens approximately 750,000 years ago? A leading explanation is that they were pushed into extinction by their closest rivals, homo sapiens (=us). And yet, modern humans of Eurasian descent have slivers of Neanderthal DNA, implying some interbreeding. One likely scenario is that homo sapiens males conquered a band of homo neanderthalensis, killing the males and taking the females.^[2]

In the Bible, this is what Pharaoh suggests doing with the enslaved Hebrews:

^{שמות א:כב} וַיְצַו פַּרְעֹה לְכָל עַמּוֹ לֵאמֹר כָּל הַבֵּן הַיִּלּוֹד הַיְאֹרָה תַּשְׁלִיכֻהוּ וְכָל הַבַּת תְּחַיּוּן.

^{Exod 1:22} Then Pharaoh charged all his people, saying, “Every boy that is born you shall throw into the Nile, but let every girl live.”

The implication here is that the Egyptians would then take the Israelite women for themselves. But Pharaoh isn’t the only one in the Torah to suggest such an approach for enemies; we find a similar option in Deuteronomy’s laws of war.

Conquering Enemies Outside the Land

The law begins with the Israelite army heading to another land to do battle (Deut 20:1–9), and then describes an Israelite siege against a foreign city. First, the Israelites must offer the city the option to surrender (Deut 20:10–11), which, if accepted, will prevent any bloodshed. If this appeal is rejected, however, the soldiers are to kill all the adult males:

^{דברים כ:יב} וְאִם לֹא תַשְׁלִים עִמָּךְ וְעָשְׂתָה עִמְּךָ מִלְחָמָה וְצַרְתָּ עָלֶיהָ. ^כ:יג וּנְתָנָהּ יְ־הוָה אֱלֹהֶיךָ בְּיָדֶךָ וְהִכִּיתָ אֶת כָּל זְכוּרָהּ לְפִי חָרֶב.

^{Deut 20:12} If it does not submit to you peacefully, but makes war against you, then you shall besiege it; ^20:13 and when YHWH your God gives it into your hand, you shall put all its males to the sword.

The women and children are part of the booty upon taking the city, along with livestock and other valuable items:

^{דברים כ:יד} רַק הַנָּשִׁים וְהַטַּף וְהַבְּהֵמָה וְכֹל אֲשֶׁר יִהְיֶה בָעִיר כָּל שְׁלָלָהּ תָּבֹז לָךְ וְאָכַלְתָּ אֶת שְׁלַל אֹיְבֶיךָ אֲשֶׁר נָתַן יְ־הוָה אֱלֹהֶיךָ לָךְ.

^{Deut 20:14} You may, however, take as your booty the women, the children, livestock, and everything else in the town, all its spoil. You may enjoy the spoil of your enemies, which YHWH your God has given you.

While it is understandably disturbing for modern readers of the Hebrew Bible to find explicit commands to annihilate foreign peoples and take their women and children as spoils, pre-modern societies worked with a different notion of morality.

An Evolutionary Perspective on Morality

The common-sense understanding of "morality," which is largely paralleled in academic discourse, is to determine "morality" in terms of prosocial behavior such as altruism, cooperation, etc. However, evolutionary approaches to morality recognized long ago that just 'being nice' doesn't cut it in natural conditions where only the strong survive. As such, the survival of a group dictates that individuals cultivate two opposing (but complementary) tendencies: just as it requires cooperation and self-sacrifice (altruism) for the benefit of the in-group, so too it often requires hostility and self-sacrifice (heroism) in defense against hostile out-groups.^[3]

To be clear, I am discussing "morality" from a descriptive perspective, i.e., identifying the criteria by which human beings distinguish a given behavior as right or wrong. It does not advance a prescriptive conclusion, which would involve proposing what should constitute right or wrong behavior.^[4]

Although humans are uniquely destructive in war, genocidal violence is also found among other animals. Jane Goodall observed chimpanzees in the 1970s systematically killing rival males, absorbing the surviving females and offspring into their own group.^[5] Similar patterns appear in human warfare, where rival males are often targeted to neutralize threats, and women are captured as reproductive resources.

Yet some conflicts aim at complete annihilation, including women. This can happen when enemy groups are culturally similar and closely connected, where the killing of women prevents the continuation of the enemy’s culture and identity.^[6] Richard Dawkins, famous for his "selfish gene" theory, introduced the concept of “memes”—units of culture like songs, fashions, or ideas—that spread by imitation, much like genes spread biologically.^[7]

Later thinkers built on Dawkins’ theory, highlighting how culture evolves in flexible, diverse ways. For example, dual inheritance or gene-culture coevolution theory suggests that human behavior results from a continuous interaction between our genes and our culture, with each influencing the other.^[8] By factoring in the cultural aspects, it becomes clear why the tendency in ancient warfare was to be especially brutal with societies that were contiguous and shared the land. The continuation of the laws of war in Deuteronomy illustrates this point.

Culturally Motivated Genocide

The requirement to first offer surrender and the limiting of killing to males applies only to fighting a war outside Israelite territory against enemies that are not Canaanites:

^{דברים כ:טו} כֵּן תַּעֲשֶׂה לְכָל הֶעָרִים הָרְחֹקֹת מִמְּךָ מְאֹד אֲשֶׁר לֹא מֵעָרֵי הַגּוֹיִם הָאֵלֶּה הֵנָּה.

^{Deut 20:15} Thus you shall treat all the towns that are very far from you, which are not towns of the nations here.

For the local peoples, no surrender is permitted, nor are the Israelites permitted to allow any to live. It must be total annihilation:

^כ:טז רַק מֵעָרֵי הָעַמִּים הָאֵלֶּה אֲשֶׁר יְ־הוָה אֱלֹהֶיךָ נֹתֵן לְךָ נַחֲלָה לֹא תְחַיֶּה כָּל נְשָׁמָה. ^כ:יז כִּי הַחֲרֵם תַּחֲרִימֵם הַחִתִּי וְהָאֱמֹרִי הַכְּנַעֲנִי וְהַפְּרִזִּי הַחִוִּי וְהַיְבוּסִי כַּאֲשֶׁר צִוְּךָ יְ־הוָה אֱלֹהֶיךָ.

^20:16 But as for the towns of these peoples that YHWH your God is giving you as an inheritance, you must not preserve anything that breathes. ^20:17 You shall annihilate them—the Hittites and the Amorites, the Canaanites and the Perizzites, the Hivites and the Jebusites—just as YHWH your God has commanded.

Requiring the elimination of the Canaanite peoples here is not only for the biological survival of the in-group but for the exclusivity of its cultural values:

^כ:יח לְמַעַן אֲשֶׁר לֹא יְלַמְּדוּ אֶתְכֶם לַעֲשׂוֹת כְּכֹל תּוֹעֲבֹתָם אֲשֶׁר עָשׂוּ לֵאלֹהֵיהֶם וַחֲטָאתֶם לַי־הוָה אֱלֹהֵיכֶם.

^20:18 so that they may not teach you to do all the abhorrent things that they do for their gods, and you thus sin against YHWH your God.^[9]

The law of the neighboring nations does not result from ethnic motivations, but fear of that the Israelites may be influenced by the forms of worship practiced by the natives, including their gods. This is stated clearly earlier in Deuteronomy, as part of the Moses’ introductory speech:

^{דברים ז:א ז:ב} ...הַחֲרֵם תַּחֲרִים אֹתָם לֹא תִכְרֹת לָהֶם בְּרִית וְלֹא תְחָנֵּם. ^ז:ג וְלֹא תִתְחַתֵּן בָּם בִּתְּךָ לֹא תִתֵּן לִבְנוֹ וּבִתּוֹ לֹא תִקַּח לִבְנֶךָ. ^ז:ד כִּי יָסִיר אֶת בִּנְךָ מֵאַחֲרַי וְעָבְדוּ אֱלֹהִים אֲחֵרִים וְחָרָה אַף יְ־הוָה בָּכֶם וְהִשְׁמִידְךָ מַהֵר.

^{Deut 7:2} …you must doom them to destruction: grant them no terms and give them no quarter. ^7:3 You shall not intermarry with them: do not give your daughters to their sons or take their daughters for your sons. ^7:4 For they will turn your children away from Me to worship other gods, and the YHWH’s anger will blaze forth against you and He will promptly wipe you out.

This passage leaves behind a purely materialistic, naturalistic motive of biological survival, requiring the killing of the Canaanites for the “higher” purpose of eliminating their cultural threat.^[10] Indeed, rhetoric bragging about such ruthless conquests was far from exceptional in the ancient Levant.^[11] In fact, in the victory stele of the Egyptian pharaoh Merenptah (1208 B.C.E.), the first historical mention of Israel purports to be its last: “Israel is laid waste, its seed is not.” ^[12]

Mesha’s Ḥerem

Another striking example comes from the Moabite Mesha inscription (ca. 840 B.C.E.), which depicts wholesale slaughter of the Israelite inhabitants of Nebo, as commanded by the Moabite god Kemosh:

^{כתובת מישע יד–יז} ויאמר. לי. כמש. לכ. אחז. את. נבה. על. ישראל | ואהלך. הללה. ואלתחם. בה. מבקע. השחרת. עד. הצהרם | ואחזה. ואהרג. כלה. שבעת. אלפן. גברן. ו[גר]ן | וגברת. וגרת. ורחמת | כי. לעשתר. כמש. החרמתה |

^{Mesha Inscription 14–17} Now Kemosh said to me, “Go seize Nebo from Israel.” So I went at night and fought against it from the break of dawn until noon. I seized it and killed everyone of [it] – seven thousand men, boys, women, gi[rls] and maidens, for I devoted it (hḥrmth) to Ashtar-Kemosh.^[13]

By referring to the ongoing conflict with the Israelite tribes, characterized by a chain of invasions and counter-attacks, Mesha insinuates the underlying rationale for the brutality of ancient warfare, namely the fear of retribution. Without external international peace-brokers, the only reliable way to escape being at the losing end of the escalating cycle of attacks and reprisals is to either completely decimate one's rivals or deter them from any future conflict.

In this case, even the women and children are killed.^[14] Perhaps the extreme nature of this destruction is due to Mesha believing that this was Moabite territory that he was retaking from the Israelites. If so, this connects with the next part of the law of war in the Torah, what to do with the local inhabitants of Canaan once they are conquered. Indeed, the last term, החרמתה, employs the hiphʿil verbal form of ḥ-r-m in an analogous manner to the Torah’s law of what to do with local enemies.^[15]

The Rhetorical Aims of 'Genocidal' Texts

That the distinction between distant and local is mentioned half-way into the war legislation and not at its beginning has led scholars to draw the convincing conclusion that the ḥerem law (vv. 15–18) as a later addition representing a more extreme ideologically driven attitude.^[16] In other words, if the law of conquest is part of the core of Deuteronomy, dating to around the 7^th century B.C.E., the ḥerem law is even later, dating to the exilic (or post-exilic) period, and this is likely the case for related texts. Indeed, virtually all contemporary scholars understand that the “genocidal” texts were composed several centuries after the period they describe, i.e., the events of the formative period of ancient Israel in the early Iron Age.

What was the rhetorical function of this emphasis on annihilating native Canaanites in a time period when these Canaanites were a distant memory?

Yair Hoffmann (1937–2019) of Tel Aviv University, who situates these passages in Deuteronomy and related texts in the Book of Joshua to the post-exilic period, argues that these texts sought to undermine the fierce polemic against Ezra-Nehemiah's ban on mixed marriage. He claims, rather ironically, that these 'genocidal' texts sought to neutralize the mixed marriage dispute by arguing that the native Canaanites have already been exterminated, so that there is no reason to worry about intermarriage.^[17] This explanation, however, is hard to square with the aggressive tone of the texts themselves, which hardly sound like a plea for tolerance.

An Idealized Past of Total Conquest

Instead, these passages seem to rework older biblical traditions to present an idealized version of Israel’s past—one in which the people are commanded to fully separate themselves from foreign nations and their religions and they do so. We already noted how the addition of the requirement to slaughter all the inhabitants of local cities (vv. 15–18) reworked an older law that was about conquest and allowed for surrender. Similarly, Deuteronomy 7 reshapes an earlier passage that describes God sending an angel to drive out the Canaanites.^[18]

^{שמות כג:כג} כִּי יֵלֵךְ מַלְאָכִי לְפָנֶיךָ וֶהֱבִיאֲךָ אֶל הָאֱמֹרִי וְהַחִתִּי וְהַפְּרִזִּי וְהַכְּנַעֲנִי הַחִוִּי וְהַיְבוּסִי וְהִכְחַדְתִּיו. ^כג:כד לֹא תִשְׁתַּחֲוֶה לֵאלֹהֵיהֶם וְלֹא תָעָבְדֵם וְלֹא תַעֲשֶׂה כְּמַעֲשֵׂיהֶם כִּי הָרֵס תְּהָרְסֵם וְשַׁבֵּר תְּשַׁבֵּר מַצֵּבֹתֵיהֶם.

^{Exod 23:23} When My angel goes before you and brings you to the Amorites, the Hittites, the Perizzites, the Canaanites, the Hivites, and the Jebusites, and I remove them, ^23:24 you shall not bow down to their gods in worship or follow their practices, but shall tear them down and smash their pillars to bits.

In Deuteronomy, this task of eliminating the native populations is given directly to the Israelites:

^{דברים ז:א} כִּי יְבִיאֲךָ יְ־הוָה אֱלֹהֶיךָ אֶל הָאָרֶץ אֲשֶׁר אַתָּה בָא שָׁמָּה לְרִשְׁתָּהּ וְנָשַׁל גּוֹיִם רַבִּים מִפָּנֶיךָ הַחִתִּי וְהַגִּרְגָּשִׁי וְהָאֱמֹרִי וְהַכְּנַעֲנִי וְהַפְּרִזִּי וְהַחִוִּי וְהַיְבוּסִי שִׁבְעָה גוֹיִם רַבִּים וַעֲצוּמִים מִמֶּךָּ. ^ז:ב וּנְתָנָם יְ־הוָה אֱלֹהֶיךָ לְפָנֶיךָ וְהִכִּיתָם הַחֲרֵם תַּחֲרִים אֹתָם... ^ז:ה כִּי אִם כֹּה תַעֲשׂוּ לָהֶם מִזְבְּחֹתֵיהֶם תִּתֹּצוּ וּמַצֵּבֹתָם תְּשַׁבֵּרוּ וַאֲשֵׁירֵהֶם תְּגַדֵּעוּן וּפְסִילֵיהֶם תִּשְׂרְפוּן בָּאֵשׁ.

^{Deut 7:1} When YHWH your God brings you to the land that you are about to enter and possess, and He dislodges many nations before you—the Hittites, Girgashites, Amorites, Canaanites, Perizzites, Hivites, and Jebusites, seven nations much larger than you—^7:2 and YHWH your God delivers them to you and you defeat them, you must doom them to destruction… ^7:5 Instead, this is what you shall do to them: you shall tear down their altars, smash their pillars, cut down their sacred posts, and consign their images to the fire.^[19]

Unlike the focus of Ezra and Nehemiah on ethnic purity, these texts in Exodus and Deuteronomy focus on religious purity, exclusive cultic devotion to YHWH and destruction not of the Canaanite cultural markers but of the people themselves.^[20]

Critical Reading of the Bible’s Genocidal Texts

The rhetorical purpose of these passages about annihilating the local Canaanite population is to emphasize the importance of maintaining a certain type of national identity. These texts promote a total war against foreign cults, aiming to solidify allegiance to the national God.^[21]

At the end of the day, however, readers must confront the fact that parts of the Hebrew Bible espouse a program of violent jihad. The modern reader may take some comfort from the fact that Jewish tradition, already from rabbinic times, sought to limit – and even eliminate – the relevance of these texts for contemporary observance.^[22]

Finally, we, as moderns, who are troubled by these ḥerem texts, need to remember that in their ancient context, they were expressions of the realities of primitive warfare. They are rooted not in what we would call ethics, but as part of a calculus dictated by evolutionary pressures, which seeks to negotiate between empathy and self-preservation in hostile circumstances. Keeping these things in mind allows ancient texts to speak for themselves without insisting they dictate contemporary moral norms.^[23]