Is Our Sin Nature Embedded in Our Mammal Nature?

Consider the parallels in the long table in this post. It reveals who we are. God’s gigantic global project for us humans is to lift us out of our mammal-sin nature and recover the image of God in Christ.

Here is an excerpt from C.S. Lewis just after Nazi Germany invaded Poland. He delivered this sermon at the Church of St. Mary the Virgin, Oxford, Autumn, 1939. He closes his sermon with these words:

All the animal life in us, all schemes of happiness that centered in this world, were always doomed to a final frustration. In ordinary times only a wise man can realize it. Now the stupidest of us know. We see unmistakable the sort of universe in which we have all along been living, and must come to terms with it. If we had foolish un-Christian hopes about human culture, they are now shattered. If we thought we were building up a heaven on earth, if we looked for something that would turn the present world from a place of pilgrimage into a permanent city satisfying the soul of man, we are disillusioned, and not a moment too soon. But if we thought that for some souls, and at some times, the life of learning, humbly offered to God, was, in its own small way, one of the appointed approaches to the Divine reality and the Divine beauty which we hope to enjoy hereafter, we can think so still. (source, emphasis added)

We humans have a lot of “animal life in us.” Can we rise above it? Let’s explore this idea more thoroughly.

There are two theories as to how we have our sin nature. One is that it is imputed to us from Adam, by virtue of his being our federal head. We are in Adam, and he is in us. “Therefore, just as sin entered the world through one man, and death through sin…” (Rom. 5:12)

The second is that it is imparted to us from our parents through genetics, from Adam (or humankind) to now. Sin is in our genes. “… and in this way death came to all people, because all sinned” (Rom. 5:12). Death came because all of us sinned, not because Adam’s sin was imputed to us.

This post explores the second theory with additional information. Just take this post for what it is: a tentative, exploratory musing. If you are a new believer or get easily confused and upset, click out now.

Image of God in humans

The Bible says we are made in God’s image (Gen. 1:26-27; Gen. 9:6).

One more time for emphasis and clarity:

Humans are made in the image of God.

Yet science says and our own experience proves that we are mammals.

We fit the classic definition: “A warm-blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, females that secrete milk for the nourishment of the young, and (typically) the birth of live young” (Source).

1. All humans are mammals.

2. You and I are humans.

3. Therefore, you and I are mammals.

Does Scripture support the fact that we are mammals?

Let me letter the main points of Scripture for clarity and conciseness.

Old Testament

A.. Gen. 2:7 says God formed humankind (’adam) from the dust of the ground, and Gen. 2:18 says God formed all the wild animals and birds out of the ground. Whether you take those two verses literally or figuratively, they teach that humans and mammals are made of the same substance.

B.. The Hebrew noun zakar (pronounced zah-kahr) means “male” in contrast to the generic “man” (used 82 times). It can refer to male offspring of humans (Lev. 12:2; Is. 66:7; Jer. 20:15) and animals (Exod. 12:5; Lev. 1:3, 10; 22:19).

C.. The Hebrew noun for soul or life or consciousness is nephesh (used 757 times), and both animals and humans can have it (Gen. 1:20-21, 24, 30;  2:7, 19; 9:4, 10, 12, 15, 16). Even the Revelation says that creatures of the sea have “life” (Rev. 8:8; 16:13).

D.. The sons of Korah have this apt comparison: “People who have wealth but lack understanding are like the beasts that perish.” (Ps. 49:20)

E.. The psalmist compares his enemies to prowling and howling pack of dogs in Jerusalem:

14 They return at evening,
    snarling like dogs,
    and prowl about the city.
15 They wander about for food
    and howl if not satisfied. (Ps. 59:14-15)

F.. The psalmist sees himself as a brute beast, when he had lacked wisdom: “I was senseless and ignorant; I was a brute beast before you” (Ps. 73:22)

G.. When the wise man Agur thought he lacked human understanding, he described himself in this way: “Surely I am only a brute, not a man; I do not have human understanding” (Prov. 30:2).

H.. In Solomon’s opinion, he wrote: “As for humans, God tests them so that they may see that they are like the animals” (Eccl. 3:18).

I.. Jeremiah compares the lust in humans to she-camels in heat offering themselves to he-camels and wild donkeys looking to breed (Jer. 2:23-24). The prophet also compares humans with the “lust” in horses: “They are well-fed, lusty stallions, each neighing for another man’s wife” (Jer. 5:8; 13:27). He saw the similarities in the breeding lust between humans and nonhuman mammals.

J.. Jerusalem is compared to a lusty woman, in stark, mammalian terms: “There she lusted after her lovers, whose genitals were like those of donkeys and whose emission was like that of horses.” (Ezek. 23:20).

Some could object that those verses in the OT are metaphors and similes, which must not be taken literally. In reply, those metaphors and similes reveal the parallels between humans and nonhuman mammals, comparisons that cannot be easily written off.

Now let’s move to the New Covenant Scriptures, where everything is upbeat and positive–or is it?

New Testament

A.. Paul warned Titus that Cretans can fall into their baser nature: “One of Crete’s own prophets has said it: “Cretans are always liars, evil brutes, lazy gluttons.” (Titus 1:12)

B.. Peter writes that degraded humans are irrational animals, born with natural instincts: “… They are like unreasoning animals, creatures of instinct, born only to be caught and destroyed, and like animals they too will perish” (2 Pet. 2:12). Then he goes on to compare them to dogs that return to their vomit, and washed sows that go back to wallowing in mud (v. 22).

C.. Jude also says that humans outside of life in the Spirit follow “mere natural instincts”: “and the very things they do understand by instinct—as irrational animals do—will destroy them” (v. 10). And “these are the people who divide you, who follow mere natural instincts and do not have the Spirit” (v. 19)

D.. Scripture often compares human mammals to sheep (Ezek. 34:11-12, 15; Matt. 9:36; 10:6; 18:12-13).

E.. The Greek word for physical “flesh” is sarx (used 147 times), though there may be differences in the flesh of one mammal to the next (1 Cor. 15:39). In some contexts, it is sometimes translated as “sin nature” because the contexts warrant it (Rom. 6:6:19; 7:5; 18, 25; 8:3-9, 12-13; Gal. 5:16-19). So it could be that the biblical authors saw that the sin nature resides in the flesh, perhaps the brain or the “heart” and body, where our internal nature is expressed outwardly.

F.. The Greek word for “body” is sōma (used 142 times), and it can be used of humans and animals (Jas. 3:3; Matt. 5:29; 6:22; 26:12).

G.. Paul writes that our earthly nature is the source of our urges to do wrong. “Put to death, … therefore, whatever belongs to your earthly nature: sexual immorality, impurity, lust, evil desires and greed, which is idolatry” (Col. 3:5). The Greek literally reads, “on the earth,” so our earthly body has some defects.

H.. Here is a sample verse that connects the flesh and the body with sin: “For if you live according to the flesh (sarx), you will die, but if by the Spirit you put to death the misdeeds of the body (sōma), you will live” (Rom. 8:13).

Now let’s apply these biblical data.

Parallels between nonhuman and human mammals and then God’s higher calling

This table shows the parallels between nonhuman mammals and humans and bad behavior and most importantly how God calls humans to restore his image and follow his higher calling to have souls filled with righteousness.

The clearest and most direct way to change the human condition is biblical revelation, the third column.

Nonhuman Mammals

Human Mammals

God’s Higher Calling

Male chimps in a troop kill a stranger chimp. Some humans, usually males, murder. You shall not murder (Ex. 20:13).
Male troops of chimps wander and threaten and kill other primates. Some humans form gangs and threaten and kill citizens and other gangs. Get rid of all … rage and anger, brawling …  (Eph. 4:31).
Various mammals (and birds) take food that they did not gather or kill. Some humans steal. You shall not steal (Ex. 20:15).
Some females abandon newborn. Some females abandon newborns (and even abort them before birth). I am like a weaned child with its mother; like a weaned child I am content (Ps. 131:2). Though my father and mother forsake me, the LORD will take me up (Ps. 27:10).
A juvenile elephant regularly rampages and kills other animals until reserve wardens put in a big bull, and the juvenile no longer kills or rampages. Some juvenile males rampage without father figures, until fathers come into juveniles’ lives. Absalom revolted: You love those who hate you and hate those who love you. You have made it clear today that the commanders and their men mean nothing to you. I see that you would be pleased if Absalom were alive today and all of us were dead (2 Sam. 19:6).
A baby monkey throws a fit when it is being weaned. A small child throws a fit because he does not get his way. Folly is bound up in the heart of a child, but the rod of discipline will drive it far away (Prov. 22:15).
Stronger monkeys bully weaker ones. Stronger people bully weaker ones.  You bully, you! At last you have what was coming to you! (Is. 14:4, NLT). Let the weakling say, “I am strong!”  (Joel 3:10)
Elephants in “Herd “A” kidnap a baby elephant from “Herd B,” and the matriarch and other females of “Herd B” struggle to get it back. Some people kidnap children. If someone is caught kidnapping … the kidnapper must die (Deut. 24:7).
Koko the gorilla, trained to communicate with a human trainer, lied in saying that her kitten damaged items in her enclosure. Some people lie. A wicked person listens to deceitful lips; a liar pays attention to a destructive tongue  (Prov. 14:5).
Male mammals spray and rub to mark territory. Some teen boys spray-paint to mark territory. Ex. 22:1-15 is all about protection of property
Some kill offspring of another family of same species (e.g. wolf kills pups of another wolfpack) Some people kill children. You shall not murder (Ex. 20:13).
Some mammals kill offspring from another male (e.g. lions, taking over a pride, kill cubs of previous males). Some stepparents mistreat and even kill stepchildren. Fathers, do not exasperate your children; instead, bring them up in the training and instruction of the Lord (Eph. 6:4).
Some mammals unmistakably look guilty, like a cowering dog after it killed a chicken. Many people look guilty when they do wrong. The look on their faces testifies against them (Is. 3:9).
Male gorillas pound chest to show dominance. Some males literally pound chest to show dominance. … nor is there male and female, for you are all one in Christ Jesus. (Gal. 3:28); you, my brothers and sisters, were called to be free. But do not use your freedom to indulge the flesh; rather, serve one another humbly in love (Gal. 5:13).
Mammals can get addicted to drugs and nicotine and alcohol if fed to them, and they do not know how to stop. Chimps can learn to be chain smokers (and so on). Some people can also get addicted to those things and find it difficult to break the habit. They can become chain smokers (and so on). Do not get drunk on wine, which leads to debauchery. Instead, be filled with the Spirit (Eph. 5:18); older women [are …] not to be … addicted to much wine (Tit. 2:2).
Males and females attract. Males and females attract, can turn into lust. (Attraction is not sinful, but lust is.) But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart (Mt. 5:28).
Some mammals seem to be attracted to same sex. Some people are attracted to same sex. Neither the sexually immoral … nor men who have sex with men … will inherit the kingdom of God … And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God (1 Cor. 6:9-10).
Alpha male claims many females. “Alpha” male desires sex with many females; one religion endorses polygamy for rich male, the alpha, the “top dog.” At the beginning the Creator ‘made them male and female,’ and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh’? (Matt. 19:4-5)


Eager to show they are the alphas, males fight (or at least display) for right to breed, but they also negotiate and cooperate to win and rise to top. Climbing to top, some males fight (sometimes fist-fight) to show they are alpha male, for right to breed, but they also negotiate and cooperate to win and rise to top (though cooperation and negotiation are not sins, necessarily). Jesus called them together and said, “You know that the rulers of the Gentiles lord it over them, and their high officials exercise authority over them. Not so with you. Instead, whoever wants to become great among you must be your servant, and whoever wants to be first must be your slave— just as the Son of Man did not come to be served, but to serve, and to give his life as a ransom for many”  (Mt. 20:25-28).
Some female chimps trade sex for food. Some females sell their bodies for money. Jesus said to them, “Truly I tell you, the tax collectors and the prostitutes are entering the kingdom of God ahead of you. For John came to you to show you the way of righteousness, and you did not believe him, but the tax collectors and the prostitutes did. And even after you saw this, you did not repent and believe him (Mt. 21:31a-32).
Some males rough up females. Some males rough up females. Husbands, love your wives, just as Christ loved the church and gave himself up for her (Eph. 5:25).
Sibling rivalry can get intense. Sibling rivalry can get intense. How wonderful and pleasant it is when brothers live together in harmony! (Ps. 133:1, NLT)
Siblings sometimes fight over food. Young siblings sometimes fight over food. … and all of you are equal as brothers and sisters (Mt. 23:8).
Nonalpha chimps and other nonalpha mammals (wolves, coyotes) cheat on alpha male with nonalpha females claimed by alpha male. Men and women cheat (adultery). You shall not commit adultery.  (Ex. 20:14)
Males are less discriminating in breeding. Males are less discriminating in breeding (males visit brothels much more often than females do, if at all). Should a man take his body, which is part of Christ, and join it to a prostitute? Never! (1 Cor. 6:15, NLT).
Mammals seem to eat almost nonstop. Some people eat too much (gluttony). Do not join those who drink too much wine or gorge themselves on meat, for drunkards and gluttons become poor, and drowsiness clothes them in rags (Prov. 22:20-21).

The above table shows that God’s global project is to lift humans out of their mammal / sin nature and restore his image in them.

Further, our mammal nature may equal human sin nature, in part. At the very least our sin nature is embedded in our mammal nature, in part. If this is true, then it argues for the theology that says that original sin / mammal nature is inherited from human parents to offspring; they pass it along to children. The doctrine of original sin is sustained.

Neutral similarities

Some similarities between nonhuman mammals and human mammals are neutral.

Nonhuman females are attracted to an alpha male; human females are attracted to a human alpha male (an athlete, for example). But human females better include good, godly character in their calculations.

Female primate gestures and postures to show sexual availability; woman gestures and postures to show sexual availability. It better be in the context of marriage!

Sex hormones influence desire to breed in both nonhuman mammals and humans. (Sex in marriage is not sinful.)

Positive similarities

Some mammals sometimes do good things, like a dog showing loyalty to its owner or the alpha male, the leader of the pack. Dogs have sacrificed their lives to save their human alphas or pack members.

A TV animal documentary about a herd of elk showed that one was wounded, and another one stayed with it and chased off a lone wolf.

So nonhuman mammals and human mammals can do both bad and good actions. That’s why I need to add that our sin nature is in our mammal nature in part.

Questions and answers

1.. Does the sinful mammal nature permeate the soul and spirit of a human?

Some teachers claim that the human spirit, when it is born again, remains sinless. However, in the Hebrew view of humanity, we are a unit, whether you believe in a body, soul and spirit, or just a body and soul. Sin defiles the whole person.

2.. Do human mammals have souls?

Yes, of course, they do. The Bible affirms it everywhere, as I noted in the Scripture section. And if you believe in three parts of the human (spirit, soul, body), then each human mammal has a spirit, too. Don’t be thrown off by the word mammal. It’s just human nature, looked at from a different angle—our connection to nonhuman mammals, a well-established, undeniable, scientific  fact.

Word Study on Spirit, Soul, and Body

Is Humankind Two or Three Parts?

3.. Do nonhuman mammals have souls?

Not in the sense and to the depth that humans have soul. Both share nephesh, however.

4.. Doesn’t the Bible say we are much more valuable than nonhuman mammals (Matt. 12:12)? Are you saying that humans are merely mammals?

No, of course not. We are made in the image of God (note the emphasis in the introduction). Other mammals are not made in his image. We are of a higher order than nonhuman mammals. Our spirits-souls can communicate with God and look up to him. One theologian called us homo divinus (divine man) for that reason. But we’re talking about our sin nature in this post, and our sin nature comes from our mammal nature. Indeed, our sin nature resides in our mammal nature.

5.. Are you saying nonhuman mammals sin?

This may be a category mistake in applying guilt and sin to nonhuman animals. But sometimes they seem to exhibit a conscience, when a dog kills a chicken and looks guilty. Koko the gorilla blamed her pet kitten for damaging items in her enclosure during the night. That was a lie. Did she know it was a lie? I say yes. What do you say?

6.. How does Adam fit into the picture?

See my post 3. Adam and Evolution: Five Options

7.. So are you saying that we do not inherit sin nature from Adam?

Humanity did, if you translate Adam as his name really means: humankind. After all, the Hebrew noun ’adam is used 558 times in the Hebrew Bible, and it means humanity as a whole: men, women, children together. Only 12 times does it seem to signify the proper name Adam (Gen. 3:17; 3:20-21 [2x]; 4:1, 25; 5:1-5 [4x]; 1 Chron. 1:1 and Hos. 6:7).

So it is best to translate Adam as “humankind.”

Therefore, yes, we inherit original sin from our human / mammal nature and our broken relationship with God, and this fractured nature is passed on from one generation to the next. Sin is rooted deeply in human origins and human nature. We inherit it from humankind, because we are humankind. We are trapped in our own closed human circuit.

8.. So do humans have free will?

The answer is the same whether we say “mammal nature” or “sin nature.” Being made in God’s image gives us free will, because God is free to do the logically possible. This built-in image of God means humans have free will (or volition) to a significant degree, and they must deny their sinful nature that is embedded in their mammal nature and exercise their free will to live righteously. When they are born again, then God’s Spirit lives in them and he gives them power to overcome the power of sin.

Do I Really Know God? He Is Sovereign and Free

9.. What does this mean for the doctrine of original sin?

As noted (no. 7), the second option of the doctrine of original sin is sustained, if my thesis is true. Our sin nature flows out our mammal nature because our sin nature is embedded in our mammal nature.

10.. Where does the Fall come in?

The Fall is just one interpretation of Gen. 3, but if you must have this interpretation, then here it is: All human mammals “have sinned and fallen short of the glory of God” (Rom. 3:23). At some time in the primeval past humans fell short, though God’s original intention was for humans to know him intimately. Paul said that primitive humankind knew God, but fell away from or rejected or refused to glorify God (Rom. 1:21). That is a great description of a fall of some kind.

All humans are deficient in their saving knowledge of God, because an unbridgeable gap stands between them and God’s glory, until God bridges the gap through Christ. That’s our fall and our later redemption.

11.. What does your tentative, exploratory thesis say about Paul’s theology in Romans 5:12-21?

If we translate “Adam” as “humankind,” then Paul’s thesis is sustained: through humankind all sin and trespass and death entered the world. Death and sin are built in to humankind’s human / mammal nature. Admittedly, this may make the more restrictive Bible interpreters nervous, but I hope they will think about the exploratory thesis in this post. It solves more problems than poses.


Finally, no fear! Just because I use the word mammal does not change the entire structure of theology through and through. The word should not be scary to Christians, because they should not be afraid of scientific facts. This tentative, exploratory thesis of our mammal nature has sustained the Bible description of human sin and Paul’s argument, but with minor adjustments. These small adjustments are not a too high a price to pay for reasonable believers.

The Bible’s description of human nature is still accurate and still stands. The doctrine of original sin stands.

How does this post help me grow in Jesus?

When humans desire to be in an intimate relationship with God and to be with him in heaven, their mammal / sin nature cannot lead them to the right way. How does this intimacy happen?

They need to go through Christ. “And have put on the new self, which is being renewed in knowledge in the image of its Creator” (Col. 3:10).

Humans need redemption and salvation to rise above their pure mammal nature, their incomplete and fractured souls. God calls all humans to be redeemed and leave behind their pure mammal nature. How?

After you repent and trust in Christ for salvation and redemption, sanctification is a process to walk in holiness and righteousness. God’s Spirit lives in each human who calls on him in Jesus’s name, in order to be restored from brokenness caused by the mammal / sin nature and decisions flowing out of our moral blindness (we don’t realize we have a mammal nature that leads us astray).

God’s big global project for humanity, therefore, is to lift humans out of their mammal / sin nature and restore the image of God in them, through a personal relationship with him through Christ and by the indwelling Holy Spirit.

Finally, church father Irenaeus (flourished 175-195) said, “The glory of God is man fully alive.” When we consider that God’s big global project is to redeem humanity out of its mammal nature and restore the broken image of God, then Irenaeus’s statement is true. God is calling you, whether a believer or unbeliever, to know him better with saving faith and the indwelling of the Holy Spirit. Then you really are the glory of God because you are fully alive in Christ.


Is Our Sin Nature Embedded in Our Mammal Nature?

Christian Scientists Comment on Young Earth Creationism

Billy Graham and Evolution

Interpreting the Bible and Accommodation

Augustine Says No to Silly Interpretations of Genesis

Evolution = Intelligent Design = God’s Design


1. Genesis 1-11 in Its Ancient Religious Environment

2. Reading Genesis 1 as Originally Intended

3. Adam and Evolution: Five Options

4. Save Our Ship! Rescuing Noah’s Ark from Flood of Science

5. The Real Significance of Genealogies in Genesis 5-11


Works Cited

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