More on Providential Ecology from Herodotus and Plato

Yes, more providential ecology. Herodotus and Plato explain why some animals have many babies, others do not. Also, flying snakes.

Wise Gods

“And, it’s reasonable to suppose that divine providence, since it is wise, set things up so that all the timid and edible animals produce many offspring in order that they would not go extinct by all being eaten up; while all the savage and violent animals are able to produce only a few offspring.”

καί κως τοῦ θείου ἡ προνοίη, ὥσπερ καὶ οἰκός ἐστι, ἐοῦσα σοφή, ὅσα μὲν ψυχήν τε δειλὰ καὶ ἐδώδιμα, ταῦτα μὲν πάντα πολύγονα πεποίηκε, ἵνα μὴ ἐπιλίπῃ κατεσθιόμενα, ὅσα δὲ σχέτλια καὶ ἀνιηρά, ὀλιγόγονα.

Herodotus, Histories, 3.108.2

“[Epimetheus] devised these things, taking care that no animal species goes extinct: when he had provided them a way to avoid destroying each other, he devised protection from the seasonal weather sent by Zeus, by clothing them in thick hair and solid hides, which are enough to keep off the winter cold, and also able to ward off burning heat; and, when they go home to their lairs, these same clothes serve as a proper and natural bed-cushion for them all. And to some he gave hooves, to others claws and thick, bloodless hides. Then, he provided them with various foods: to some, grass from the earth; others, fruits from trees; others, roots. There are also those to whom he gave other animals to eat as food, and to them he bestowed few offspring, while to those consumed by them, many offspring, ensuring the survival of the species.”

ταῦτα δὲ ἐμηχανᾶτο εὐλάβειαν ἔχων μή τι γένος ἀϊστωθείη· ἐπειδὴ δὲ αὐτοῖς ἀλληλοφθοριῶν διαφυγὰς ἐπήρκεσε, πρὸς τὰς ἐκ Διὸς ὥρας εὐμάρειαν ἐμηχανᾶτο ἀμφιεννὺς αὐτὰ πυκναῖς τε θριξὶν καὶ στερεοῖς δέρμασιν, ἱκανοῖς μὲν ἀμῦναι χειμῶνα, δυνατοῖς δὲ καὶ καύματα, καὶ εἰς εὐνὰς ἰοῦσιν ὅπως ὑπάρχοι τὰ αὐτὰ ταῦτα στρωμνὴ οἰκεία τε καὶ αὐτοφυὴς ἑκάστῳ· καὶ ὑποδῶν τὰ μὲν ὁπλαῖς, τὰ δὲ <ὄνυξι> καὶ δέρμασιν στερεοῖς καὶ ἀναίμοις. τοὐντεῦθεν τροφὰς ἄλλοις ἄλλας ἐξεπόριζεν, τοῖς μὲν ἐκ γῆς βοτάνην, ἄλλοις δὲ δένδρων καρπούς, τοῖς δὲ ῥίζας· ἔστι δ᾽ οἷς ἔδωκεν εἶναι τροφὴν ζῴων ἄλλων βοράν· καὶ τοῖς μὲν ὀλιγογονίαν προσῆψε, τοῖς δ᾽ ἀναλισκομένοις ὑπὸ τούτων πολυγονίαν, σωτηρίαν τῷ γένει πορίζων.

Plato, Protagoras, 321A–B

The Mating Habits of Vipers and the Winged Snakes of Arabia*

“As for vipers and the winged snakes of Arabia, if they came about as their nature would have it, living would be impossible for human beings; in fact, however, when the vipers mate, at the very moment when the male ejaculates, once he emits the seed, the female grabs his throat, bites down, and does not let go until she has eaten through. And while the male dies in the way we just described, the female gets paid back for it by the male. Seeking revenge for their father, the offspring, while they are still in the belly, chew through their mother and eat through her womb, thus making their escape. The other snakes, however, since they are not harmful to people, lay eggs and hatch a great clutch of offspring.”

ὣς δὲ καὶ οἱ ἔχιδναί τε καὶ οἱ ἐν Ἀραβίοισι ὑπόπτεροι ὄφιες εἰ ἐγίνοντο ὡς ἡ φύσις αὐτοῖσι ὑπάρχει, οὐκ ἂν ἦν βιώσιμα ἀνθρώποισι: νῦν δ᾽ ἐπεὰν θορνύωνται κατὰ ζεύγεα καὶ ἐν αὐτῇ ᾖ ὁ ἔρσην τῇ ἐκποιήσι, ἀπιεμένου αὐτοῦ τὴν γονὴν ἡ θήλεα ἅπτεται τῆς δειρῆς, καὶ ἐμφῦσα οὐκ ἀνιεῖ πρὶν ἂν διαφάγῃ. ὁ μὲν δὴ ἔρσην ἀποθνήσκει τρόπῳ τῷ εἰρημένῳ, ἡ δὲ θήλεα τίσιν τοιήνδε ἀποτίνει τῷ ἔρσενι: τῷ γονέι τιμωρέοντα ἔτι ἐν τῇ γαστρὶ ἐόντα τὰ τέκνα διεσθίει τὴν μητέρα, διαφαγόντα δὲ τὴν νηδὺν αὐτῆς οὕτω τὴν ἔκδυσιν ποιέεται. οἱ δὲ ἄλλοι ὄφιες ἐόντες ἀνθρώπων οὐ δηλήμονες τίκτουσί τε ᾠὰ καὶ ἐκλέπουσι πολλόν τι χρῆμα τῶν τέκνων.

Herodotus, Histories, 3.108.2–3

“Megasthenes says that in India there are winged scorpions of immense size, and that their sting is similar to that of European ones. And that in the same place, there are also snakes with wings, and that they come around not during the day but at night, and they emit from themselves a urine, which, immediately produces decay when it falls on someone’s body.”

Μεγασθένης φησὶ κατὰ τὴν Ἰνδικὴν σκορπίους γίνεσθαι πτερωτοὺς μεγέθει μεγίστους, τὸ κέντρον δὲ ἐγχρίμπτειν τοῖς Εὐρωπαίοις παραπλησίως. γίνεσθαι δὲ καὶ ὄφεις αὐτόθι καὶ τούτους πτηνούς· ἐπιφοιτᾶν δὲ οὐ μεθ' ἡμέραν ἀλλὰ νύκτωρ, καὶ ἀφιέναι ἐξ αὑτῶν οὖρον, ὅπερ οὖν ἐὰν κατά τινος ἐπιστάξῃ σώματος, σῆψιν ἐργάζεται παραχρῆμα.

Aelian, Nature of Animals, 16.41

*So, I guess winged serpents are more like cobras, less like flying snakes? More curious is the contrast Herodotus implies between what an animal does by its own nature, and what it does because of divine providence. Is the idea that the divine intervenes in how animals act and interact, but doesn’t make them what they are?

Via getty images

Plato on Providence in Laws X

More on providence: the theodicy from Plato’s Laws. Plato doesn’t say the divine punishes or spites people for failing to be as virtuous as they could be. Instead, he says the cosmic ruler figures out where people with less-than-perfect characters in this life are most likely to succeed in the next one, and makes sure that’s where they end up. Didn’t make it as a good human? No problem—in the next round, maybe you can make it as a good bird or fish. The idea is that the cosmos has been set up so that we’re always given a chance to excel, not just for our own sake, but for the sake of being a part of a process of making everything as good as possible.

“Athenian: This. When the ruler of the cosmos saw that all our actions are ensouled, and that in them there is much virtue and much vice, and that soul and body, once they came into existence, were indestructible—for, had either of them been destroyed, there would never have been a generation of animals—, but they were not eternal like the customary gods, and when he saw by how much the good of the soul is always by nature beneficial, and the evil harmful—when he saw all these things, he determined where, if placed, each individual would make virtue victorious and vice defeated in the universe. And he made it so that, depending on what we are like, we must make our home always in a certain abode and ever in certain places. The causes of becoming the way we are, however, he left to our individual choices. For how we desire and what our soul is like—in just about every case, all of us for the most part come to be the way we are by this.”

ΑΘ. Ὧδε. ἐπειδὴ κατεῖδεν ἡμῶν ὁ βασιλεὺς ἐμψύχους οὔσας τὰς πράξεις ἁπάσας καὶ πολλὴν μὲν ἀρετὴν ἐν αὐταῖς οὖσαν, πολλὴν δὲ κακίαν, ἀνώλεθρον δὲ ὂν γενόμενον, ἀλλ' οὐκ αἰώνιον, ψυχὴν καὶ σῶμα, καθάπερ οἱ κατὰ νόμον ὄντες θεοί – γένεσις γὰρ οὐκ ἄν ποτε ἦν ζῴων ἀπολομένου τούτοιν θατέρου – καὶ τὸ μὲν ὠφελεῖν ἀεὶ πεφυκός, ὅσον ἀγαθὸν ψυχῆς, διενοήθη, τὸ δὲ κακὸν βλάπτειν· ταῦτα πάντα συνιδών, ἐμηχανήσατο ποῦ κείμενον ἕκαστον τῶν μερῶν νικῶσαν ἀρετήν, ἡττωμένην δὲ κακίαν, ἐν τῷ παντὶ παρέχοι μάλιστ' ἂν καὶ ῥᾷστα καὶ ἄριστα. μεμηχάνηται δὴ πρὸς πᾶν τοῦτο τὸ ποῖόν τι γιγνόμενον ἀεὶ ποίαν ἕδραν δεῖ μεταλαμβάνον οἰκίζεσθαι καὶ τίνας ποτὲ τόπους· τῆς δὲ γενέσεως τοῦ ποίου τινὸς ἀφῆκε ταῖς βουλήσεσιν ἑκάστων ἡμῶν τὰς αἰτίας. ὅπῃ γὰρ ἂν ἐπιθυμῇ καὶ ὁποῖός τις ὢν τὴν ψυχήν, ταύτῃ σχεδὸν ἑκάστοτε καὶ τοιοῦτος γίγνεται ἅπας ἡμῶν ὡς τὸ πολύ.

Plato, Laws 904A6–C4

Spontaneous Generation: Galen and Alexander against the Platonists on why the world soul doesn’t make mosquitos

Stranger: Take animals and all mortal things, and even plants, those which grow from seeds on the earth or those which grow from roots, and those bodies without soul which form in the earth, both the ones that can be melted and the ones that can’t. Surely we are not going to say anything other than divine craftsmanship makes them come to be after previously not being? Or do we consult the saying and opinion of the masses that…

Theaetetus: That what?

Stranger: That nature produces them from some spontaneous cause and without an engendering thought, rather than with reason and divine knowledge that comes from a god?

Ξένος: ζῷα δὴ πάντα θνητά, καὶ δὴ καὶ φυτὰ ὅσα τ᾽ ἐπὶ γῆς ἐκ σπερμάτων καὶ ῥιζῶν φύεται, καὶ ὅσα ἄψυχα ἐν γῇ συνίσταται σώματα τηκτὰ καὶ ἄτηκτα, μῶν ἄλλου τινὸς ἢ θεοῦ δημιουργοῦντος φήσομεν ὕστερον γίγνεσθαι πρότερον οὐκ ὄντα; ἢ τῷ τῶν πολλῶν δόγματι καὶ ῥήματι χρώμενοι—

Θεαίτητος: ποίῳ τῳ;

Ξένος: τὴν φύσιν αὐτὰ γεννᾶν ἀπό τινος αἰτίας αὐτομάτης καὶ ἄνευ διανοίας φυούσης, ἢ μετὰ λόγου τε καὶ ἐπιστήμης θείας ἀπὸ θεοῦ γιγνομένης; [265δ]

Plato, Sophist 265 C-D

“When one of my Platonists teachers told me that the soul-that-is-extended-through-the-whole-cosmos formed the (human) embryo, I thought that the technical skill and power is worthy of it; but, I could not abide thinking that the world-soul formed scorpions, poisonous spiders, flies, conopses, vipers, grubs, worms and ascarides. I take it this kind of opinion comes near impiety. ”

εἰπόντος δέ τινος τῶν διδασκάλων μοι τῶν Πλατωνικῶν, τὴν δι' ὅλου κόσμου ψυχὴν ἐκτεταμένην διαπλάττειν τὰ κυούμενα, τὴν μὲν τέχνην καὶ δύναμιν ἀξίαν ἐκείνης ἐνόμισα, σκορπίους δὲ καὶ φαλάγγια, καὶ μυῖαν καὶ κώνωπας, ἐχίδνας τε καὶ σκώληκας, ἕλμινθάς τε καὶ ἀσκαρίδας ὑπ' ἐκείνης διαπλάττεσθαι νομίζειν οὐχ ὑπέμεινα, πλησίον ἀσεβείας ἥκειν ὑπολαβὼν τὴν τοιαύτην δόξαν.

Galen, On the Formation of the Foetus, 4.700—701 K

“Again, it is possible to discover the existence of a regular order even among evil things and things that come to be contrary to nature, like abscesses, wounds, inflammations, and periodic illnesses. But also the generation of some living things is in fact orderly, without being relative to an Idea, like the generation of grubs, gnats, and grubs.”

ἔτι τὸ εὔτακτον ἔστιν εὑρεῖν καὶ ἐν τοῖς κακοῖς καὶ παρὰ φύσιν γιγνομένοις, οἷον ἀποστήματα, τραύματα, φλεγμοναί, νόσων περίοδοι. ἀλλὰ καὶ ζῴων τινῶν γενέσεις τεταγμέναι μέν, ἀλλ' οὐ πρὸς ἰδέαν, οἷον σκωλήκων, ἐμπίδων, τερηδόνων.

Alexander of Aphrodisias, On Aristotle’s Metaphysics Α, 103,35-104-19 Hayduck

Providential Ecology in Herodotus and Aristotle

(Some classic examples of thinking that divine providence is providential enough, continued from here…)

Prolific Rabbits, Savage Lions

“Well, I suppose divine providence, which is wise as far as I can tell, has made all the timid and edible animals produce many offspring so that they would not go extinct by being eaten up, while it has made all the savage and violent animals produce few offspring.

“Take the following case: the hare is hunted by everyone—beast, bird, and human. Obviously, then, it produces many offspring. It is the only creature that can conceive when it is already pregnant. Some of the young in her belly are hairy, others are bare; and some in the womb are finishing taking on their shape, others are just starting out.

“That’s one kind of case. Another is the lioness, who is very strong and bold, and bears a single cub once in her lifetime since she casts out the womb with the cub. The cause of this is the following: when the cub first begins to move about in the womb, its claws—much sharper than those of all the other beasts—tear the womb. The more it grows, the more it tears and scratches, and when it is close to being born, there is absolutely nothing healthy left of it.”

καί κως τοῦ θείου ἡ προνοίη, ὥσπερ καὶ οἰκός ἐστι, ἐοῦσα σοφή, ὅσα μὲν ψυχήν τε δειλὰ καὶ ἐδώδιμα, ταῦτα μὲν πάντα πολύγονα πεποίηκε, ἵνα μὴ ἐπιλίπῃ κατεσθιόμενα, ὅσα δὲ σχέτλια καὶ ἀνιηρά, ὀλιγόγονα. τοῦτο μέν, ὅτι ὁ λαγὸς ὑπὸ παντὸς θηρεύεται θηρίου καὶ ὄρνιθος καὶ ἀνθρώπου, οὕτω δή τι πολύγονον ἐστί: ἐπικυΐσκεται μοῦνον πάντων θηρίων, καὶ τὸ μὲν δασὺ τῶν τέκνων ἐν τῇ γαστρὶ τὸ δὲ ψιλόν, τὸ δὲ ἄρτι ἐν τῇσι μήτρῃσι πλάσσεται, τὸ δὲ ἀναιρέεται. τοῦτο μὲν δὴ τοιοῦτο ἐστί: ἡ δὲ δὴ λέαινα ἐὸν ἰσχυρότατον καὶ θρασύτατον ἅπαξ ἐν τῷ βίῳ τίκτει ἕν: τίκτουσα γὰρ συνεκβάλλει τῷ τέκνῳ τὰς μήτρας. τὸ δὲ αἴτιον τούτου τόδε ἐστί: ἐπεὰν ὁ σκύμνος ἐν τῇ μητρὶ ἐὼν ἄρχηται διακινεόμενος, ὁ δὲ ἔχων ὄνυχας θηρίων πολλὸν πάντων ὀξυτάτους ἀμύσσει τὰς μήτρας, αὐξόμενός τε δὴ πολλῷ μᾶλλον ἐσικνέεται καταγράφων: πέλας τε δὴ ὁ τόκος ἐστί, καὶ τὸ παράπαν λείπεται αὐτέων ὑγιὲς οὐδέν.

Herodotus, Histories, 3.108.2-4

Hungry Dolphins

“When it comes to the mouth, as well, there are differences among kinds of fish. Some have a mouth that goes straight across and is in the front, while others have it underneath, like dolphins and selachians. And they turn belly-up when they feed. It seems nature does this not only to preserve all the other animals (when the dolphins are turned upside down, they move slowly and the other animals can get away – all such animals are carnivorous), but also so that they are not guided by gluttony for food, since if they could get their food easily, they would be destroyed because of the rate at which they would fill themselves up.”

Ἔχει δὲ καὶ περὶ τὸ στόμα διαφοράς. Τὰ μὲν γὰρ κατ' ἀντικρὺ ἔχει τὸ στόμα καὶ εἰς τὸ πρόσθεν, τὰ δ' ἐν τοῖς ὑπτίοις, οἷον οἵ τε δελφῖνες καὶ τὰ σελαχώδη· καὶ ὕπτια στρεφόμενα λαμβάνει τὴν τροφήν. Φαίνεται δ' ἡ φύσις οὐ μόνον σωτηρίας ἕνεκεν ποιῆσαι τοῦτο τῶν ἄλλων ζῴων (ἐν γὰρ τῇ στρέψει σῴζεται τἆλλα βραδυνόντων· πάντα γὰρ τὰ τοιαῦτα ζῳοφάγα ἐστίν), ἀλλὰ καὶ πρὸς τὸ μὴ ἀκολουθεῖν τῇ λαιμαργίᾳ τῇ περὶ τὴν τροφήν· ῥᾷον γὰρ λαμβάνοντα διεφθείρετ' ἂν διὰ τὴν πλήρωσιν ταχέως.

Aristotle, Parts of Animals, 4.13, 696b24-32

Michael of Ephesus on providence and good behaviour

I'm writing a paper on Michael of Ephesus on providence. I've looked at his views on providence before, but I've started to take it a bit more seriously. Michael uses providence in a few places in his commentaries on Aristotle's biology, and he uses it, as you might expect, as a deus (natura?) ex machina to explain things Aristotle does not (maybe it's more precise to say that he uses providence to complete explanations which Aristotle had left incomplete). On the one hand, I'm interested in in figuring out what Michael thinks providence is - is it a version of the Christian God, or nature, or νοῦς? - but I'm also trying to figure out what his rules are for using it in his commentaries. The way he uses it doesn't seem to be arbitrary (there are times he doesn't use it when he could) and this makes me wonder if he's drawing on an earlier tradition, or following his own philosophical or cultural intuitions. Here is one of these appeals, about why some animals have testes and some do not. NB: I think the fact that Michael refers to providence in this passage should not distract us from what he is actually trying to do, and that is to explain animal mating behaviour in terms of the contribution the behaviour makes to the survival of the species. Also: contrary to what Aristotle and Michael say, fish and snakes do in fact have testes.

Aristotle: "Nature does everything because of necessity of because of the better..."

"If nature does everything either because of necessity or because of the better, then this part [i.e., the testicles] would also exist for one of these reasons. Now, that testicles are not necessary for generation is obvious, since then all animals that generate would have them; but in fact, snakes, birds, and fish do not have testicles, for they are observed when they are mating and they have ducts filled with milt. It remains, then, that they are present for something better. It is a fact that, for most animals, there is just about no other function than [producing] seed and fruit, as is the case for plants. And just as in matters of nutrition animals with straight intestines are more ravenous* in their desire for food, so too those that do not have testicles but only ducts, or which have testicles but have them internally, they are all quicker with respect to the activity of mating. Those animals which need to be more moderate**, just as before the intestines are not straight, also here the ducts have coils so that their desire is not either ravenous or sudden.*** Testicles have been designed for this reason, for they make the movement of the spermatic residue slower."****

εἰ δὴ πᾶν ἡ φύσις ἢ διὰ τὸ ἀναγκαῖον ποιεῖ ἢ διὰ τὸ βέλτιον, κἂν τοῦτο τὸ μόριον εἴη διὰ τούτων θάτερον. ὅτι μὲν τοίνυν οὐκ ἀναγκαῖον πρὸς τὴν γένεσιν φανερόν· πᾶσι γὰρ ἂν ὑπῆρχε τοῖς γεννῶσι, νῦν δ' οὔθ' οἱ ὄφεις ἔχουσιν ὄρχεις οὔθ' οἱ ἰχθύες· ὠμμένοι γάρ εἰσι συνδυαζόμενοι καὶ πλήρεις ἔχοντες θοροῦ τοὺς πόρους. λείπεται τοίνυν βελτίονός τινος χάριν. ἔστι δὲ τῶν μὲν πλείστων ζῴων ἔργον σχεδὸν οὐθὲν ἄλλο πλὴν ὥσπερ τῶν φυτῶν σπέρμα καὶ καρπός. ὥσπερ δ' ἐν τοῖς περὶ τὴν τροφὴν τὰ εὐθυέντερα λαβρότερα πρὸς τὴν ἐπιθυμίαν τὴν τῆς τροφῆς, οὕτω καὶ τὰ μὴ ἔχοντα ὄρχεις πόρους δὲ μόνον ἢ ἔχοντα μὲν ἐντὸς δ' ἔχοντα, πάντα ταχύτερα πρὸς τὴν ἐνέργειαν τῶν συνδυασμῶν. ἃ δὲ δεῖ σωφρονέστερα εἶναι, ὥσπερ ἐκεῖ οὐκ εὐθυέντερα, καὶ ἐνταῦθ' ἕλικας ἔχουσιν οἱ πόροι πρὸς τὸ μὴ λάβρον μηδὲ ταχεῖαν εἶναι τὴν ἐπιθυμίαν. οἱ δ' ὄρχεις εἰσὶ πρὸς τοῦτο μεμηχανημένοι· τοῦ γὰρ σπερματικοῦ περιττώματος στασιμωτέραν ποιοῦσι τὴν κίνησιν.

Aristotle, Generation of Animals 1.4, 717a12-32 (Peck's Loeb edition here)

* λαβρότερα | 'more ravenous' The word λάβρος can describe violent surges of water and wind, also people and animals. LSJ suggest 'furious' or 'violent', or 'impetuous'; Peck translates it as 'violent'. The sense, however, is clearly that the animals have strong appetites: their intestines are shorter, and without twists and turns to slow down the food and residues, they are never full for long. I like 'ravenous' here: we use it in English (although it is a bit affected) to describe strong appetites + 'ravenous' comes from the archaic ravin ('an act of rapine or robbery'), which is a direct borrowing from French ravine ('impetuosity', violence', 'force'), from which we get ravine, i.e., 'a violent rush of water' and by extension the gorge it travels through. From the Latin rapina, 'to rob', 'plunder', etc. In the Michael passage, I translate it as "(more) impulsive".

** δεῖ σωφρονέστερα | 'need to be more moderate' More of a moral term than λάβρος. Peck translates 'have to be more sober'. But it's the δεῖ that's caused people to pause: why do some animals need to be more moderate in their appetites? Why couldn't all animals be ravenous and impetuous? Aristotle does not tell us why; he just mentions that testicles cause the seminal ducts to double back, 'like stone weights on a loom (a35-6: καθάπερ τὰς λαιὰς προσάπτουσιν αἱ ὑφαίνουσαι τοῖς ἱστοῖς)'.

*** πρὸς τὸ μὴ λάβρον μηδὲ ταχεῖαν εἶναι τὴν ἐπιθυμίαν This is a statement of the final cause - testicles cause the ducts to coil in order to steady the animal's desire. The relationship between desire and lack or excess might be in the background: desire for food is an impulse to fill something that has been emptied beyond what is natural; and the desire for sex is an impulse to empty something that has been filled to excess. However, if this were the case, it's not clear to me why slower moving semen would cause an animal to have less desire. Aristotle is vague about the details of the analogy, and Michael will focus mostly on trying to make sense of it.

**** στασιμωτέραν ποιοῦσι τὴν κίνησιν Peck translates 'makes the motion steadier'. στάσιμος is an absence of κίνσις, i.e., movement as flow (e.g. Plato, Sophist 256b6-7; Hippocrates, Nature of Women 1.10). Potter translates it as 'constipated' in his Loeb translation of Nature of Women. The idea again is that the residues don't flow out as quickly as they would if the ducts were straight.

Michael on Aristotle on pudic providence

"What comes to be by nature, comes to be by necessity or the better. "Necessity" means that which is found in every kind, and without which it is not possible for something to come to be. "Better" [means] that which is not like this. Since testicles are not found in every [kind] of male, and generation also occurs without them, they do not exist because of necessity, but because of the better.

Just as, in matters of nutrition, [animals] with straight intestines are more ravenous…

"In what follows he sets out the reasons because of which, among [animals] that have testicles and do not have testicles, (i) some have them, (ii) others do not have them; and of those that have them, (i.b) some have them internally, like birds, but (i.a) others externally. He says, then, that just as "animals with straight intestines" are "more impulsive with respect to desire for food", because the residue comes out more quickly because of their straight intestines, while those that do not have straight intestines are more self-controlled and take less nourishment, "the same applies to (ii) [animals] that do not have testicles but only passages", like fish, "or (i.b) [animals] that have [testicles] but internally",  like birds. Hence, (ii) [animals] that do not have testicles at all are quicker than all other [animals] with respect to the task of mating; (i.b) while [animals] that have [testicles] internally are slower and more self-controlled with respect to this kind of task than those that do not have testicles, but they are more impulsive and faster than (i.a) the ones that have them externally.

"First, we should say why [nature] has designed some [animals] to be naturally self-controlled and has made the testicles of these kinds external, some [naturally] more impulsive and [made their testicles] internal, but others it has utterly neglected and did not assign testicles, and for this reason they are also most impulsive of all. But on this point we should say briefly that [nature] did not neglect them, but that it has regarded them by an even greater magnitude. For since (as he will say going on) they are not able to engage in contact for a long time because they live in water, [nature] has not given [them] testicles in addition to the other things (which he is going to speak about later). For in the case of animals that have testicles, the emission of semen comes about slowly because of the reasons which we will learn. But let this much have been said as an introduction. We must discuss what was mentioned, and then the cause according to which (i.a) firstly, those that have external testicles are especially self-controlled, (i.b) second those [that have] internal [testicles] are even less so, and (ii) most undisciplined of all are those that do not have any [testicles]. And so, we must move on to Aristotle's answer.

"One should note that since nature desires that animals and all other things exist eternally and aims at this, whatever things were not able to be preserved eternally as the same thing numerically, for them [nature] decreed eternity by means of always generating others from others. But since continuous mating causes dissolution of the body* for reasons he will mention in the present book when he talks about what the nature of semen is—since then [continuous mating] imparts weakness, and it is normal for death to follow dissolution in the majority of cases, all those animals that naturally bear few offspring (he will also talk about the reasons for their bearing few young in the present book and in those that follow this one)—all those, then, that naturally bear few offspring have come to be more self-controlled than the others by nature's forethought, so that the animals are not dissolved and destroyed by mating many times each day, and this kind of animal is not suddenly eradicated. Those animals that bear offspring, but [bear] more than those that bear few and a fewer number than those that bear very many, are less moderately self-controlled than those that bear few offspring. For even though they [i.e., the individual animals] should happen to be destroyed from frequent mating, still, because of the fact that they bear more than two or three offspring (it is sometimes possible [for them to bear] even more than seventeen**), such a kind will not be left out of the whole. For this reason, then, [nature] designed these to be less self-controlled. But those that bear altogether many offspring, what necessity is there to regard them? For it is clear that they will not be lacking, since heaps of them are produced. This, then, is the reason that some are more self-controlled, others less, and others not at all."

τὰ δὲ ὑπὸ τῆς φύσεως γινόμενα τὰ μὲν γίνεται διὰ τὸ ἀναγκαῖον, τὰ δὲ διὰ τὸ βέλτιον. ἀναγκαῖον δὲ λέγεται τὸ ἐν ἅπαντι τῷ γένει εὑρισκόμενον, καὶ οὗ ἄνευ οὐκ ἐνδέχεται γενέσθαι τι, βέλτιον δὲ τὸ μὴ τοιοῦτον. ἐπεὶ δὲ οἱ ὄρχεις οὔτε ἐν ἅπαντι τῷ τῶν ἀρρένων εὑρίσκονται γένει, γίνεται δὲ γένεσις καὶ χωρὶς αὐτῶν, οὔκ εἰσι διὰ τὸ ἀναγκαῖον, ἀλλὰ διὰ τὸ βέλτιον.

[35] 717a23 «Ὥσπερ δὲ ἐν τοῖς περὶ τροφὴν τὰ εὐθυέντερα λαβρότερα.»

Ἐντεῦθεν τὰς αἰτίας ἐκτίθεται, δι' ἃς τὰ ἔχοντα ὄρχεις καὶ τὰ μὴ [6.1] ἔχοντα τὰ μὲν ἔχει, τὰ δ' οὐκ ἔχει, καὶ τῶν ἐχόντων τὰ μὲν ἐντὸς ἔχει, ὥσπερ οἱ ὄρνιθες, τὰ δ' ἐκτός. φησὶν οὖν ὅτι, ὥσπερ «τὰ εὐθυέντερα λαβρότερά» ἐστι «πρὸς τὴν ἐπιθυμίαν τῆς τροφῆς» διὰ τὸ θᾶττον ἐξέρχεσθαι τὸ περίττωμα διὰ τὴν εὐθυεντερίαν, τὰ δὲ μὴ εὐθυέντερα σωφρονέστερα καὶ [5] ὀλιγοτροφώτερα, «οὕτω καὶ τὰ μὴ ἔχοντα ὄρχεις, πόρους δὲ μόνον», ὡς οἱ ἰχθύες, «ἢ ἔχοντα μὲν ἐντὸς δέ» [717a23-25], ὡς οἱ ὄρνιθες· τὰ μὲν οὖν μηδ' ὅλως ἔχοντα ὄρχεις εἰσὶ πρὸς τὴν ἐργασίαν τοῦ συνδυασμοῦ ταχύτερα πάντων, τὰ δ' ἔχοντα μὲν ἐντὸς δὲ βραδύτερα πρὸς τὴν τοιαύτην ἐργασίαν τῶν μὴ ἐχόντων ὄρχεις καὶ σωφρονέστερα, λαβρότερα δὲ καὶ ταχύτερα τῶν αὐτοὺς [10] ἐχόντων ἐκτός.

ῥητέον δ' οὖν ἡμῖν πρῶτον μέν, τίνος ἕνεκεν τῇ φύσει πεφρόντισται τοῦ τὰ μὲν εἶναι σώφρονα καὶ πεποίηκε τῶν τοιούτων τοὺς ὄρχεις ἐκτός, τὰ δὲ λαβρότερα καὶ ἐντός, τῶν δὲ καὶ παντελῶς κατωλιγώρηκε καὶ οὐκ ἀπέδωκεν ὄρχεις, καὶ διὰ τοῦτό εἰσι καὶ πάντων λαβρότατα. ῥητέον δὲ πρὸς τοῦτο συντόμως ὅτι οὐδὲ τούτων κατωλιγώρησεν, ἀλλὰ καὶ [15] μᾶλλον κατὰ πολὺ πεφρόντικεν· ἐπειδὴ γὰρ ἐν ὕδατι ὄντα οὐ δύνανται ἐπὶ πολὺ ἐνδιατρίβειν, ὡς καὶ αὐτὸς προϊὼν ἐρεῖ, τῇ ἁφῇ, οὐ δέδωκε πρὸς τοῖς ἄλλοις οἷς μέλλει λέγειν λόγοις περὶ τούτων ὄρχεις· ἐν γὰρ τοῖς ἔχουσιν ὄρχεις βραδεῖα δι' ἃς μαθησόμεθα αἰτίας ἡ πρόεσις τοῦ σπέρματος γίνεται. ἀλλὰ τοῦτο μὲν οὕτως προλελέχθω· ἡμῖν δὲ τὰ εἰρημένα ῥητέον καὶ ἔτι [20] τὴν αἰτίαν καθ' ἣν συμβαίνει πρώτως καὶ μάλιστα σώφρονα εἶναι τὰ ἐκτὸς ἔχοντα τοὺς ὄρχεις, δευτέρως δὲ καὶ ἧττον τὰ ἐντός, πάντων δὲ ἀκολαστότατα τὰ μηδ' ὅλως τούτους ἔχοντα· καὶ οὕτως τὴν Ἀριστοτέλους ῥῆσιν μετιτέον.

ἰστέον οὖν ὡς ἐπειδὴ ἡ φύσις τοῦ ἀεὶ εἶναι ζῷα καὶ τὰ ἄλλα πάντα ἐφίεται καὶ τούτου στοχάζεται, ὅσα οὐκ ἠδυνήθη φυλάξαι ἀεὶ τὰ [25] αὐτὰ τῷ ἀριθμῷ, τούτοις ἐπρυτάνευσε τὴν ἀιδιότητα διὰ τοῦ ἀεὶ ἄλλα ἐξ ἄλλων γίνεσθαι. ἀλλ' ἐπεὶ ὁ συνδυασμὸς ὁ συνεχὴς ἔκλυσιν τοῦ σώματος ἐμποιεῖ δι' ἃς ἐρεῖ αἰτίας ἐν τῷ παρόντι βιβλίῳ, ὅταν περὶ τῆς φύσεως τοῦ σπέρματος λέγῃ τίς ἐστιν, ἐπεὶ οὖν ἔκλυσιν ἐμποιεῖ, τῇ ἐκλύσει δὲ φιλεῖ ὡς τὰ πολλὰ παρέπεσθαι θάνατον, ὅσα τῶν ζῴων ὀλιγοτόκα πέφυκεν [30] (ἐρεῖ δὲ καὶ τῆς τούτων ὀλιγοτοκίας τὰς αἰτίας ἐν τῷ παρόντι βιβλίῳ καὶ ἐν τοῖς ἐφεξῆς τούτου) ὅσα οὖν πέφυκεν ὀλιγοτόκα, γέγονε σωφρονέστερα τῶν ἄλλων προνοίᾳ φύσεως, ὅπως μὴ πολλάκις τῆς ἡμέρας συνδυαζόμενα ἐκλύηται καὶ φθείρηται καὶ τάχιον ἐκποδὼν γένηται τὸ τοιοῦτον γένος. ὅσα δὲ τίκτει μέν, ἀλλὰ πλείω μὲν τῶν ὀλιγοτόκων, ἐλάττω δὲ κατὰ πολὺ [35] τῶν πάνυ πολλὰ τικτόντων, ἧττόν ἐστι σωφρονέστερα τῶν ὀλιγοτόκων· εἰ γὰρ καὶ συμβαίη αὐτοῖς φθορὰ ἐκ τοῦ πολλάκις συνδυάζεσθαι, ἀλλὰ διὰ τὸ [7.1] πλείω τοῖν δυοῖν καὶ τριῶν τίκτειν, ἔστι δ' ὅτε καὶ τῶν ἑπτὰ καὶ δέκα, οὐκ ἐπιλείψει τὸ τοιοῦτον γένος ἐκ τοῦ παντός. διὰ τοῦτο οὖν ἧττον ἐφρόντισε τοῦ σώφρονα εἶναι ταῦτα. τῶν δὲ πάμπαν πολλὰ τικτόντων τίς ἡ ἀνάγκη τούτων φροντίσαι; δῆλον γὰρ ὡς οὐκ ἐπιλείψουσι σωρηδὸν γινό[5]μενα. ἡ μὲν οὖν αἰτία τοῦ τὰ μὲν εἶναι σώφρονα μᾶλλον τὰ δ' ἧττον τὰ δ' οὐδ' ὅλως αὕτη.

Michael of Ephesus, In de generatione animalium commentaria 1.4 (CAG 14.3, 5,35-7,6 Hayduck)

*ἔκλυσιν τοῦ σώματος | dissolution of the body.  The idea is not articulated in Aristotle in quite the way Michael thinks it is, but it's a common belief that too much sex will weaken and destroy the body.

**ἔστι δ' ὅτε καὶ τῶν ἑπτὰ καὶ δέκα.   This is rather specific.