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Ancestor Math

A Family History Activity

How many great-great-grandparents do you have?

Don't Google it. We're going to do the math — and the answer is going to blow your mind.

Press → or tap Next to begin

Part 1 of 12

It Starts With You

Let's count backward, one generation at a time.

You have 2 parents. Each of them had 2 parents. That gives you 4 grandparents.

Each of those 4 had 2 parents — 8 great-grandparents.

See the pattern? Every generation back, the number doubles.

Part 2 of 12

The Doubling

How fast does it grow? Drag the slider and find out.

Generations back from you

5

Years per generation:

32 3rd great-grandparents

62 total ancestor slots (all gens combined)

1901 approximate year

— world population then

Part 3 of 12

The Big Number

Ready for this?

0

ancestor slots at generation 30 — your 28th great-grandparents
(~750 years ago)

Over 1 billion ancestor slots — in a single generation. But in 1276, the entire world had only 390 million people.

How can you have more ancestors than people who existed?

Part 4 of 12

Pedigree Collapse

The answer: the same person shows up more than once in your tree.

Imagine your great-great-grandmother on your mom's side is also your great-great-grandmother on your dad's side. One person, two slots. This is pedigree collapse — and the further back you go, the more it happens.

Your tree gets wider. The population gets smaller. Eventually they crash into each other.

Ancestors vs. World Population

Generations: 20

Gen 1 = parents, Gen 2 = grandparents, Gen 3 = great-grandparents. Each bar compares your ancestor count to the world population.

Under population Exceeds population (collapse guaranteed)

Part 5 of 12

The Human Family

A brief history of everyone who ever lived.

"And Adam called his wife's name Eve; because she was the mother of all living."Genesis 3:20

We believe all humans descend from common parents. Science agrees — in a different way — that all living humans share common ancestors going back thousands of years.

Adam & Eve The garden. The beginning of the human family.

Noah & the Flood 8 souls survived. Every person alive descends from Noah's family. Faith-fact: there are 8 primary human blood types (A+, A−, B+, B−, AB+, AB−, O+, O−). Eight survivors, eight blood groups.

Tower of Babel Languages confused, families scattered across the earth.

Lehi's Family Departs A small family leaves Jerusalem for a promised land.

Birth of Christ ~300 million people on earth. The Savior's mortal ministry begins.

The Black Death Killed ~30-60% of Europe. World population dropped by an estimated 75-100 million.

The First Vision 1 billion people on earth. The restoration of the Gospel begins — and with it, the work of turning hearts to our fathers.

Elijah Returns Elijah appears in the Kirtland Temple, restoring the sealing keys (D&C 110). Family history work can now begin in earnest.

FamilySearch Goes Online The largest genealogical database in the world becomes freely accessible to everyone.

You. Right Now. 8.1 billion people alive — and every one of them is your cousin. You are part of this story.

Part 6 of 12

Generations to the Prophets

How far back are you from the great figures of scripture?

At ~25 years per generation, here's how many generations separate you from each one:

~9

Joseph Smith Born 1805 — The Restoration. Just 9 generations ago. Your 7th great-grandparents were his contemporaries.

1805

~81

Jesus Christ ~1 AD — Luke chapter 3 traces His lineage 77 generations back to Adam. You're roughly 81 generations from Him.

~1 AD

~81

Peter, James & John Same era — The Apostles who restored the Melchizedek Priesthood to Joseph Smith across ~72 generations.

~30 AD

~137

Moses ~1400 BC — Led Israel out of Egypt. The law of Moses governed your ancestors for over 50 of those generations.

~1400 BC

~161

Abraham ~2000 BC — Father of the covenant. If you've received a patriarchal blessing declaring lineage, you are counted among his descendants.

~2000 BC

~161

                        The 12 Tribes of Israel
                        Jacob's 12 sons — the roots of all Israelite lineage. Your patriarchal blessing names your tribe. Most Latter-day Saints: Ephraim or Manasseh.
                    
~1900 BC

~177

Noah ~2400 BC — 8 survivors. Every person alive descends from his family. 177 generations — and only 10 from Adam to Noah (Genesis 5).

~2400 BC

~217

Enoch ~3400 BC — Built a city so righteous it was taken up. His people are the City of Enoch — Zion.

~3400 BC

~241

Adam & Eve ~4000 BC — The beginning. ~241 generations from you to the first parents of the human family.

~4000 BC

The math check: 2²⁴¹ ancestor slots at Adam's generation is a number with 72 digits. Obviously, pedigree collapse means the same ancestors fill countless slots. By the time you reach Noah (~177 generations), the entire human family funnels through just 8 people.

Faith-fact: Adam to Noah is only 10 generations (Genesis 5). Noah to Abraham is another 10 (Genesis 11). Abraham to Christ is ~42 (Matthew 1). The biblical record compresses thousands of years into surprisingly few generations because early patriarchs lived centuries.

Part 7 of 12

What This Means

Scientists estimate the most recent common ancestor of all living humans lived just 3,000 to 5,000 years ago. Your family tree and everyone else's already overlap.

For people in the same community? Go back just 6 to 7 generations — that's the 1800s — and you almost certainly share an ancestor with the person sitting next to you.

Everyone in this room is family.

"Have we not all one father? Hath not one God created us?"Malachi 2:10

When we do family history, we're not just finding names — we're reconnecting links in one human family that goes all the way back to the beginning.

"And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers."Malachi 4:6

Activity Break

Relatives Around Me

Let's prove it. Right now.

Everyone in this room is family — let's find out how.

1

Open the Family Tree app on your phone (by FamilySearch)

2

Tap More (bottom right) → Relatives Around Me

3

Tap Scan for Relatives — enable Bluetooth if prompted

4

Tap a name to see how you're related!

Time remaining

3:00

What to expect: Most matches land around 9th to 11th cousins. That means your shared ancestor lived roughly 10–12 generations ago — right around the 1600s–1700s, when the early colonists were settling in the New World. That's pedigree collapse in action: many of us share those same colonial-era ancestors, which is why the connections show up so often. And remember — within your own ward or community? Probably just 6 to 7.

No app? Go to familysearch.org/discovery/relatives-at-reunions on any browser. You can also pair up with someone who has the app!

Raise your hand when you find a connection. Who's the closest relative in the room?

Part 9 of 12

Cousin Decoder

Ever wonder what "second cousin once removed" actually means?

Try these — or enter your own numbers

Person A (generations from ancestor)

Person B (generations from ancestor)

1st Cousins

The cousin number = whoever is closer to the ancestor, minus 1. Both 3 away? 3 − 1 = 2nd cousins.

"Removed" = different generations. Your mom's 1st cousin is your 1st cousin once removed.

Fun fact: You and your best friend? Probably 10th cousins or closer. Everyone of the same ethnicity is at most a 16th cousin.

Part 10 of 12

Your 64

Let's make this personal.

Six generations back — your 4th great-grandparents — 64 people. All alive around the mid-1800s.

Each one had a name. A face. A favorite food. Something that made them laugh. Some crossed oceans. Some survived wars. Some joined the Church and gave up everything to gather to Zion.

You exist because all 64 of them existed.

Most people can name 2 or 3 of their 64. The rest are waiting — in records, in archives, in temples — for someone to find them.

"We without them cannot be made perfect; neither can they without us be made perfect."Doctrine & Covenants 128:18

That someone could be you. This week. Right from your phone.

Quick math check

2 parents

4 grandparents

8 great-grands

16 2nd greats

32 3rd greats

                        64
                        4th greats
                    

126 total slots
(all 6 gens)

How many can you name?

Part 11 of 12

Your Turn

Three things you can do this week.

1

Ask a grandparent (or parent) for the names of their grandparents. That's 4 generations — 16 ancestor slots you can start filling in. Record it in your phone right then.

2

Log in to FamilySearch and see how far back your tree goes. Find one ancestor you've never heard of. What was their life like?

3

Take a name to the temple. Use the "Ordinances Ready" feature on FamilySearch to find an ancestor whose temple work needs to be done — and go do it.

Get Started

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My Family Tree See your pedigree on FamilySearch

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Discovery Activities Fun, bite-sized family history activities

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Ordinances Ready Find names ready for the temple

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Relatives at Reunions See how you're related to friends

Every name matters. Every link matters. That's why we do this work.